Johnson, Evinrude, OMC, outboard motor, outboard motor repair, 9.5 hp, date/year of manufacture, water pump, carburetor,

 Maintaining Johnson QD Series 10 hp
2 cycle outboards

1949 1963   (Information & normal repairs)   


This 10
hp motor, was built from 1949 to 1963, which was a the last of the high profile 10 hp series motors.   It spans the gap of being made by Johnson and then on into the merger with Evinrude in 1956 when the OMC company was formed.

These motors appear to be made in two different external configurations.  Those made from 1949 to 1958 as shown in the LH photo above.  And then the later style 1959 to 1963 which utilized a more modern cowling as shown in the RH photo.  It appears that the main motor and everything but the cowling is the same.  The cowling for 1960 and 61 had a gold raised ring on top like the photo on the upper right of this header.   In 1959 the lower unit was downsized to the same as the 15hp.   And from 1960 on, the motor was fitted with a fuel pump instead of the pressurized tank with Siamese hoses as were used previously.

There was a companion 15 and 18 hp motors made at about the same time as the early QD with a model # FD which was very similar and also shared many parts.

The year of manufacture for these models of motors are listed in the chart below.   Apparently the first four years of production model numbers did not stop at the calendar year end.   It also appears that the long-shaft motors were not made until 1957 after OMC was formed a year earlier.    The "L" in the model number designates it being a Long Shaft. 

Another bit of information if the ID plate is missing is the color of the engine may help as to the year,  1949 - 55 metallic Green,  1956 - 58 metallic Red,  1959 - 63 White.

Year Model Year Model
 1949-50  QD-10   QD-11  1951-52  QD-12   QD-13
 1953  QD-14  1954  QD-15
 1955  QD-16  1956   QD-17
 1957  QD-QDL-18  1958  QD-QDL-19
 1959  QD-QDL-20  1960  QD-QDL-21
 1961  QD-QDL-22  1962  QD-QDL-23
 1963  QD-QDL-24    

If you need to check on parts and do not have a actual parts list booklet, one of your best sources is http://www.crowleymarine.com/   They have a complete listing of about all of the Johnson and Evinrude motors showing exploded parts views with part numbers.  Here you may be able to order parts online from them.  Or this one http://www.marineengine.com/parts/parts.html.       Or to Boat info 1922-1964 Johnson Service Manual

 

Go to your local NAPA automotive store.  They have a marine products catalog that shows #18-5181 replacement coil that is supposed to fit  1949-1963 10hp Johnson.   Looking farther, it is a pretty standard coil that fits many other motors from 1.5hp up to 30hp.  They also show points and condensers.  The tune-up kit (the whole set of 2 points and 2 condensers) is #18-5006.   

You will not find many aftermarket internal parts for these motors in the NAPA or Sierra catalogs apparently as this motor dates too far back.   Here is a link to a website that has considerable info on these old motors  CLICK HERE

Recommended Fuel / Oil Mix :   These old 10 hp since 1949 were built without needle bearings in the crank and rods, wrist pin bushings were bronze.  Fuel/oil mix on all these older OMC motors that have bronze rod bearings is 24-1 of the old 30 weight automotive motor oil.  Now it would be the TCW-3 standard outboard oil, which would give better oiling and longer motor life than the automotive oil originally recommended for this motor.

The 7.5hp and smaller of the same years all had babbit bearing rods and brass bushing crank journals, so you do want to at least stay with the richer 16:1 mix on those.

On most all of the pints and quart plastic bottles of TWC-3 oils there will be a narrow clear vertical window on the edge of the bottles.  On the sides of this window will have numbers representing ounces and Milliliters for other parts of the world.  Or you can purchase special measuring containers showing different ratios and the amount of ounces needed.

This is one of those  motors where you have to mix the oil with the gasoline, so you need to know how much gas you will be needing, add the oil before you fill the fuel tank so that the oil mixes better that just dumping it in after you fuel up.  However if that is not possible, then guess, add a majority of what you think it will take, top off the tank and then add the rest matching the amount of gasoline you took on.  If you are using portable fuel thanks, before hand, when you fill it, add 1 gallon at a time, use a clean 3/8" or 1/2" dowel start filling the tank, mark the dowel at each gallon you add, then you can use it as a measuring stick.  This way you can refill a partly full tank with the known amount of oil.

A quart has 32 ounces of oil in it. 

FUEL MIXING TABLE

Gallons of Gasoline

Gasoline to Oil Ratio

Ounces of Oil to be Added

16:1 24:1 32:1 50:1 100:1
1 8 5 4 3 2
2 16 11 8 5 3
3 24 16 12 8 4
4 32 21 16 11 6
5 40 27 20 13 7
6 48 32 24 16 8

Now the recommended fuel is 87 octane gasoline. Early on for the 2 cycle motors the recommended oil was regular automotive 30 weight motor oil, then the outboard industry came up with any TWC oil, which finally evolved into the latest which is TWC-3 outboard motor oil. You probably will not see much of the older TWC-2 oil out there anymore.  You can spend your money and purchase OMC oil for about $6.50 a quart, or buy a name brand quart for $3.59. Sure the manufacturers want you to buy their oil, and for a new motor under warranty, it may be advisable to do so.  But the consensus from many experienced boaters is to use any good brand of oil, as long as it has the TWC-3 rating, it meets or exceeds the manufacturers specifications.  The TWC-3 represents, Two cycle, Water Cooled, type 3 formula.  The formula 3 has decarbonizing additives designed to be more compatible with the newer non-leaded fuel.

So from the above information, you can see that fuel and oils have changed dramatically since these motors were first brought out.  In this instance, times have changed for the good, as we now have a better gasoline along with way better outboard oils.

DO NOT use oil designed for your weed whacker or chain saws as these air cooled motors run a lot hotter than the water cooled outboards.   The outboards require the specially designed TWC-3 oils.

Here is an example of a QD crankshaft, what can & does happen if the oil mix is too lean,  more like probably here there was no oil mix in the fuel at all

Recoil Starter :  These motors have a recoil starter mounted on top over the flywheel that is bolted to the block by two bolts in the front sides and one in the rear.  The starter pawl is attached to the rope spool by a couple of unique springs that are activated as the rope is initially pulled as seen in the photo below.  The spool is held into the housing by a single bolt in the middle coming up from the bottom.  The rope appears to be 9/32 diameter, however the smaller 1/8" could be used. 

The spring usually has a long life.  However if it breaks, it is pretty straight forward in replacing it.   Sometimes if a spring breaks and has broken a few inches off, you can heat the end up with a propane torch, enough to make a new bend, which may work OK.

A trick that is often used to modify the spool for ease of replacing the rope, is take a Dremel tool and grind a shallow groove on the lower lip of the starter spool, as seen by the red arrow below (any location will do and will vary depending on the length of the rope).  Grind just enough to allow the rope to be pulled into and then be rotated around between it and the housing.  To wind the spring tighter, pull the rope out a couple of feet, rotating the spool to where this groove is in line with the rope exit hole to the knob.  Reach in with a small screwdriver or crochet hook, pull the rope out and into this groove.  Now you can pull the rope more, winding the spool tighter with this rope secured in the groove, which allows you to add spring tension easily without jumping through hoops of getting things right before you bolt it back onto the housing.

I do read "arrow here rope recoiled " and below that model numbers of JE or F.   Since I do not have a service manual for this motor, I am not really sure what that means.

Rope pulled into hand ground groove to facilitate winding rope onto spool

 

Left side showing throttle linkage Right side of the 1960 motor showing manual starter,  carburetor, air breather, fuel pump & shifting lock-out directly in front of the fuel pump
 

There appears to be no provision for electric start on these motors.

 Flywheel :   As for removing the flywheel, unless it is rusted on, loosen the nut a few turns so it protrudes slightly above and protecting the crankshaft threads, wrap your arm around the flywheel, putting tension (raising the motor), rap the nut sharply with a 2 or 3# hammer, (brass preferably).  The weight of the motor hanging by the flywheel will usually allow the flywheel to pop off the taper. 

The only markings I find on the flywheels are " set point .020".

This flywheel has a inspection cover that allows you to go through the hole to adjust the points without removing the flywheel, as seen at the red arrow below.  This cover is held in place by three screws that also serve as flywheel puller attachment holes.  There is another screw holding the outer edge in place.  The flywheel nut is independent of this cover plate.

You will notice the two large hook type dog teeth, which is where the starter pawl engages.

Top view of flywheel Bottom side of flywheel

Ignition :  This series of motors used a magneto ignition system with points and condenser ignition which shared common parts with many of the other Johnson motors of the same era.  The coils, especially those in the 60's motors have a reputation for cracking and allowing moisture in and then starting to break down, creating problems.  They changed the plastic formulation on the coils at some stage and the replacement ones are fine.   About 60% of the old motors I have had needed one or more coils replacing, and would be financially unviable for someone not working on their own motor.

A lot of people will replace the coils without replacing the spark plug leads.  Even if they do, often times the connection from the coil to the spark plug lead is not very good.  The faces of the coils also have to be lined up with the machined face perfectly or you're spark will not be perfect.  Those who run the old spark plug leads after changing the coils will often overlook the spark plug boot connections too.

To adjust the points some versions have a  "inspection hole" in the top of the flywheel,  if so you do not have to remove the flywheel but can adjust the points thru this hole.  If you do need to replace the points, you will need to remove the flywheel however.   On some of these models (especially the early ones) they may have a spring loaded cam on the crank shaft.   Or with the flywheel off, remove spring to install or set the points then use a thin screwdriver to hold the cam down while putting the flywheel 'mostly' on.   On these if you do take the flywheel off,  you may find it hard to get the flywheel back on because it is hard to get this cam to stay down while reinstalling the flywheel.   (1) Use screwdriver to hold the cam down while putting the flywheel on, and if you're quick, it works.  You may wish you have an extra set of hands though, or call a buddy over.  (2) Or turn the shaft/cam to where it is just short of starting to open one set of points.  Then the cam will slide down without interference.  Now your ready to torque it on.  Not too bad once you get the hang of it. 

One old time mechanic had a suggestion.  If you are setting the points with the flywheel off, you may find that holding this cam down while setting the points is a bother.  You can made a short piece of tubing to hold the cam down while setting the points. The flywheel nut holds the tubing down, tubing holds the cam down.

Double check your points gap, .020, anything more or less may throw timing off enough not to fire.  These need to be set at the highest part of the cam lobes and if off just a slight bit can effect timing.

Timing plate showing ignition system & one bad coil


In the photo below you can see the burned out coil from the above photo.  Replacement ignition parts are still available.  They do not have a lot of power on only one cylinder.

Burned out coil

Kill Button :  The kill button is mounted in the lower front cowling on the right hand side.

Kill button shown on the exterior with the actual sealed connections inside

Recommended Spark Plugs : The recommended spark plug is a Champion J6J, now J6C, however with a well used motor most old time mechanics would recommend a hotter plug, like the J8C especially if you do a lot of trolling.    Or if you opt for the NGK brand, go for BR6S-8.   These plugs use the 3/8" reach, so do not try to use the 1/2" reach ones off the 9.9hp as the electrodes will become smashed by the top of the piston.

Twist Grip Throttle Handle :  The twist grip and throttle uses cog gears similar to the earlier series motors.

Low Speed Stop Screw :  These motors (at least the post 59 models) have an adjustable stop screw on the bottom gear at the end of the rod that moves the advance mechanism (base of the handle).

This adjustable stop screw shown at the arrow can be adjusted to bump against the boss in front of it

Fuel Pump :   On the motor that I had access to for this article (a 1960 version) had the fuel pump bolted to the top by-pass cover which used the standard single hose fuel line.    The 35hp and the Fat Fifty was really the only motors that had fuel pumps up to and including 1959.   Everything else was pretty much all pressure tank models.   All these 10hp  motors made prior to 1960 would have had the older pressurized Siamese type dual fuel line.   However, a fuel pump kit was offered as an accessory on 10hp and up motors as it would be needed for boats with built-in fuel tanks.    

If you are having problems and the indications point to fuel, double check the fuel lines or fittings/tank for leaks.  The older tanks are pressurized while the newer single line tanks operate on a vacuum.

1960 fuel pump side view 1960 fuel pump rear view showing by-pass cover

 

Here is the original fuel pump disassembled Here is the same fuel pump but the parts flopped over

The fuel filter/sediment bowel does not really need to be there, but since it was already mounted, I just left it, re-routed the fuel lines to and from it.

To convert the older motors to a fuel pump here is a LINK on how I did one.

Another Method : If you can not find one of the newer bypass covers, one can be made from a piece of 3/16" aluminum as shown below, which converts over to the newer small square 1965-1985ish fuel pumps.

Here is made up an aluminum adapter plate for the newer style fuel pump conversion

 Thermostats :  These show in the parts manuals to be the same from 5hp to 55hp for years 1959 to 1994.   They may have slightly different configurations because of improvements, but they will all function no matter the shape or design.   They can usually be removed and cleaned up with no problems, UNLESS they are really contaminated because of debris or salt corrosion.  Do not run outboard motors without a thermostat.

Here the thermostat cover is removed showing the thermostat on the top LH side of the head

Oil Tube for Top Main Bearing :   There is a brass tube located on the LH side of the block at the juncture of the intake manifold to the block.  It transports oil from the bottom to the top main bearing.   All of the fuel that the motor burns passes through the crankcase on it's way to the cylinders.  This oily fuel is what lubricates the internal parts.  Most of it goes right through, carried along with the airflow to the cylinders.  But a bit of it "rains" out or splatters up against the walls then drains down settling at the lower main bearing.   There is collection pocket around this lower bearing housing. This oil collected in the bottom pocket is pumped to the top main bearing by the alternating suction/pressure of the action of the 2 cycle operation.  It is all accomplished by taking advantage of the different pressures in the crankcase.  There is no mechanical pump like what you would find in a four-stroke.

The oil transfer tube is shown here by the screwdriver on the port side of the motor

 No Overboard Water Indicator :  These motors were made before the common "pee hole" indicator was being used.   There was just a "blubber hole" on the rear upper exhaust housing where some of the exhaust gasses mixed with some of the used cooling water from the engine.

This model appears that it could be converted to a overboard water indicator (pee hole) style by using the same basic method of tapping overboard water off the top of the thermostat housing as used on my conversion of the 6hp motor.

Carburetor :   These carburetors have both high speed and idle jets that are adjustable.  In the photos below of the pre 1959 version there is are individual separated knobs for for both the high speed and low speed adjustments placed vertically on the front cowling with the choke on the Port side. 

Here a QD-19  (1958) shown from the rear with the breather boxes.  Note the fuel filter on the bottom of the carburetor Here the same QD-19 showing the front panel with separate high speed & low speed knobs

The front motor panel of this later 1960 version shown below has a dual knob in the center.  The outer knob is the high speed adjustment which is marked from 1 to 6.  The (supposed to be red) inner knob is the idle adjustment.  The choke is in the normal Starboard side of this panel. 

The timing plate cam on this version angles downward as it extends to fast position.  The cam roller is mounted on the front of the intake manifold, (shown in the photo below) instead of on the carburetor tops like the later ones are.

The basic carburetor is pretty much the same, for the pre-and post 59s but the linkage is different.

Front view showing timing cam & roller Control panel for a post 59 motor showing both high & low speed jet adjustments with the choke knob on the left

These carburetors have a built in glass fuel filter / settling bowl at the bottom.  The air breather, (they call it the air box) is attached to the front of the carburetor.  The choke knob is screwed onto the brass linkage rod from the front.  The nuts holding the carburetor onto the manifold use a 1/2" wrench.  You have to pull the choke out to access the RH nut with the wrench.

When you take it apart, it is advisable to count the outward revolutions of both of these needle jet shafts so you have an idea as to were to return them to.  These floats are made of varnished cork.  Unless the motor has been stored with old gas in the carburetor, the float should still be usable.  The float level is set so the float is parallel with the body when turned upside down.  This is done by bending the brass tab at the rear of the needle for the shut off.

ANOTHER thought, if the motor is having starting problems, these motors won't start if the high speed needle is adjusted wrong.  When turned to the start position for cold start it's the high speed part of the carburetor that comes into play here, not the low.   Also make sure your stem packing is new for both, and that the main jet is backed out enough for it to fire as described below.

In the photos below you can see the bottom or high speed jet along with it's linkage to the control knob. The knob operating this jet slides over a octagon sleeve around the idle jet shaft.  The low speed needle which is the top one, screw it in to a lightly seated position and back out 1 1/2 turns.  The high speed needle which is the bottom one is 3/4 turn out from lightly seated position.   Run it in gear under load (at a fast run), adjust high speed in until it starts to die then back out until it runs smooth. Slow down to idle and adjust low speed in until it slows down or starts to cough and back off until it smoothes out.  You can loosen the high speed linkage rod and adjust the linkage so that the dial is set where you want it.  I also like to slip the low sped knob onto the shaft so the pointer is pointing straight up.  That's all there is to it.   

If you are having starting problems, and you are sure the ignition is OK, fuel or the choke may not be operating properly for cold start.  Spray come mixed fuel into the carburetor and see if she fires off.

If you are having problems with the high and low speed needle shafts being loose and backing out while running changing the adjustment, there is a "packing nut" around the shafts at the point where they enter the carburetor (as seen in the photos below).  Tighten these nuts to put more tension on the shafts, (righty tighty-lefty loosy).

Anyway, it shouldn't take more than 10 minutes to pull the intake manifold and check the reeds to see if a bug or whatever is blocking them open.  But they're rarely the problem and the problem can be pointed to if it won't crank at all without fuel being sprayed directly into the cylinders via the plug holes.

 
Right side view of a 59 Left side view of a 59

As this series advanced, the factory made changes, (with this series probably having underwent the most cosmetic surgery of all the other models).  The previous models utilized the carburetor dual knob system with center knob as the idle adjustment and the lower knob as the high speed adjustment.  As seen in the RH photo below, this is reversed with the high speed in the center.  This is because the main motor cowling was changed, putting these adjustment knobs in the lower part of the cowling instead of higher in a separate front panel.  Now the high speed adjustment is directly in line with lower needle (high speed), instead of using a linkage rod to activate it.

  Front view of a 1963 model
 

Reed Valves :   Stuck open reeds will keep the motor from being able to push fuel into the crankcase, thereby preventing it from starting.  However, stuck open or closed reeds will have no effect on compression because the compression reading is off the top side of the piston.   The reeds open and close, sucking fuel into the crankcase from the carburetor because of the osculating suction/pressure off the bottom side of the pistons.

If it's bad reeds, the motor should still crank up and start momentarily if fuel mix is sprayed directly into the spark plug holes.  If you decide to pull the manifold to check the reeds, be very careful if you choose to pull the intake that you remove every screw!  There are a couple of hard ones to spot inside the manifold that must be removed before it will come off.  If you pry on the manifold with much force you are guaranteed to ruin it.  However I wouldn't pull it unless it will start with fuel in the cylinders, but not without it.

Motor Mounts :   The rubber motor mounts are pretty well designed, a rubber block with attachment bolts molded into them last a long time and are externally mounted.  The actual runner mount is the same for both the upper and lower, but the lower has a housing around it that also clamps onto the pivot shaft as shown in the photos below.

Upper motor mounts Lower motor mounts behind the cover

Upper Cowling Mounts :  These rubber mounts are susceptible to breaking, especially the rear ones as the rear of the cowling is what is normally used to help lift the motor up and puts a lot of strain on these rear mounts.  These tend to have the bonding from the bolts to the rubber deteriorate and may separate from the mounting bolts.    It is also rather hard to remove the usually rusted nuts from the bolt studs to even try to re-bond the rubber.  The originals are made of a thick round rubber that has a stud screw bonded to both the top and bottom.  If you have the powerhead off, you could make replacement ones from 1/4" all-thread and some thick rubber, about 5/8" (I am guessing here as to get to them it takes pulling the power-head).  Otherwise it is probably the best would be to try to clean them and then use Super Glue. 

They are usually just left alone unless you are doing  are rebuild with the powerhead off.   Leaving them broken, the result is not detrimental to the running of the motor, except the upper cowling when snapped to the lower part has some movement and can make a rattling noise when running.

QD cowling mounts

Clamp Bracket Screws :   These screws that hold the motor to the boat transom threads are  1/2" X 13 TPI or National Course.  If you can not find any replacement ones then a simple 1/2 NC bolt  3" long or with at least 2" of threads and with a flat washer under the threaded end will suffice for a considerable time.  It may just not be a pretty looking as the original, but it will hold the motor to the boat.  Most of these screws are damaged by neglect of not maintaining them with a small amount of chassis grease or Vaseline before they rust or corrode in the bracket.

Shown in the photo below is a built in location to use a chain from the motor to the boat for safety sake.

QD clampscrews

Gearbox :   If it runs pretty much OK in neutral, but bogs down in any gear, then possibly you have a lower unit / gearbox problem.   Unscrew the large headed slotted screw (not the Phillips screw) in the bottom area of the lower unit.  What comes out?  There should be a dark thick gear oil.   If it is a thick creamy color it has water inside.  If no oil comes out, your unit has a leaky shaft seal, which may have let water in and then over time also drained out if not ran for some time.  If this is the case then you may have a rusty prop shaft or gears.  Either of these will put a lot of excess resistance on the motor when shifted into either forward or reverse, causing it to bog down.

The lower unit gearbox is not the unitized type as used on the later 9.9s but has a bottom section that when the unit is turned upside down, exposes all the gears and output shaft.  There is a spaghetti type O-Ring that seals the grease in the lower unit when assembled.

The gear box was changed in 1958 from the larger 5 bolt lower unit to a smaller 4 bolt unit.    Also there was a internal change in how the pinion gear (drive gear in the gearbox) was attached to the driveshaft with it being changed from a friction fit onto the driveshaft to a splined fit.   It appears that all the other gears, shaft and bearings remained the same.  This change came about 1959/60, as 1960 parts list shows 2 different part numbers for the pinion gear.

Here the gearbox is removed from the motor & the lower 1/2 also removed showing the gears & shaft bearings.  Note the 3/16" hole in the shifting yoke.  This is where the Allen headed PIVOT screw goes thru.

To install the new seal, be sure the hole in the bearing housing is clean, lay the housing endways (front down), align the new seal, start it by hand if possible.  Then lay a flat piece of steel on the seal, tap it in with a hammer.  This way it can only go in as far as the housing allows as the flat steel will stop because it is hitting the housing.

When you reassemble the shaft and shifting slider dog, be sure that the slider yoke is positioned as shown above.  Also the bearing housing has a hole that engages a peg in the upper housing that secures it and keeps it from rotating, be sure that is in the right place before you tighten down the cover.

This gear case does not use a regular gasket, but a spaghetti rubber seal is .100" dia. allowing the two metals to mate tightly.  This seal is purchased in bulk so you cut off just a bit more than you need.  For this model 11" is enough. This seal is the same as used on all the other models that have the split gearbox, it may just be a different length depending on the size of the motor.  It may do the job alone, but OMC recommended it's 3M 847  sealant, but it's kind of pricey hard to find at regular stores.  Lots of folks use Permatex Ultra Black with good success and it's available at almost any auto store for just a few bucks. The main thing is that you want to keep it watertight.   Also when you lay out the rubber seal in the groove, cut off just a little longer than needed as it will spread out in groove when housing is pressed together.

When reassembling these gear cases, you should use some gasket sealant on the spaghetti seal itself, both surfaces of the clamshell gear case as well, especially around the bolt holes as well as the perimeter of any oil seals.

The old 10 hp prior to 1958 had the larger 5 bolt lower unit which were the same as the 15's and 18's had in that same era.   

Here the 5 bolt gearcase is shown, note the stud on the rear, being the 5th bolt.  The 4 bolt units do not have this rear stud 

 

There was a internal change in how the pinion gear (drive gear in the gearbox) was attached to the driveshaft with it being changed from a friction fit onto the driveshaft to a splined fit.   It appears that all the other gears, shaft and bearings remained the same.  This change came about 1959/60, as 1960 parts list shows 2 different part numbers for the pinion gear.

If your motor slips out of gear, you either are missing the shifter lock detent bar on the side of the powerhead, your clutch dog and gears are worn out, or the shift linkage is worn out. Or all three.

Shown here are the shaft & gears from a QD 23 with the teeth missing from the friction fit pinion gear.  Here you can see the sliding clutch dog between the forward & reverse gear Here the drive (forward ) gear clutch dog engagement notch is worn as evidenced by the shiny corner area
 

If you have heard that a worn clutch dog can be flopped 180 degrees and use the old reverse engagement ears as forward, -- NO NOT REALLY, same surface but on the different gear.  This MAY help as a temporary slight fix IF the gears are worn like the one above but the dog is still good, which is usually not the case as both are normally pretty well worn by the time you tear it apart.

Water Pump Repair :   This water pump impeller replace job is a simple remove 4 bolts at the lower unit to mid housing.    To access the shifting lever coupler when removing the lower unit, there is a small cover on the right hand side of the exhaust housing retained by a screw top and bottom.  Remove this cover then you can then get to the coupler and remove the bottom screw to disengage the upper shifting rod from the lower rod in the lower unit.  Now the lower unit should drop down and be loose from the rest of the motor.

In replacing this screw upon reassembly be careful to get the groove that the screw goes into centered in the screw hole before you attempt to insert and tighten down the screw.  The one I worked on had a tendency to slide up too far which could bind the screw when it was tightened, stripping the threads.  A flashlight and slow movement of the shift lever is needed in this situation.

Access cover in place on the RH side of the mid-section Access cover removed, showing shifter rod coupler screws

Water pumps are basically the same design as still used on all outboard motors.  These impellers are a larger diameter than on some of the later unitized lower units, in my book they appear to be able to still function even after many years of usage even after becoming less flexible.  The one thing the early units,  was that they were made of a pot-metal cast housing that after years of neglect, the normal deteriorated condition it will be well worn or corroded inside (as shown below).  It is then recommended to replace the pump unit with the newer nylon housing with a stainless steel liner version if you have plans on keeping this motor in your stable for some time.

10 hp impeller installed in an older pot metal upper housing before final assembly

One thing that is a good idea is that the water pump outlet tube's lower end that goes into the water pump grommet is cut at a slight angle.  This facilitates this tube being inserted into the grommet so that the grommet does not get folded over, partially blocking the water flow from the water pump.

There appears to be a change in 1958 with a different lower unit which included the water pump and impeller when the cowling was also changed.  These used what was known as the 4 bolt lower unit.  The earlier impeller is the same as the 10, 15 and 18 hp of the same years.  The 1958 and newer are the same as the 9.5 hp series which followed this model.  The impeller used on these later motors  is 2 3/4" in diameter, 1/2" thick, with a 9/16" shaft hole and has 6 vanes.

In the LH photo below, note the nylon O-Ring at the top of this pump housing.  This slides into the motor's mid-section and ensures shaft alignment..   The black color water pump housing is just a painted pot metal unit as seen at the upper O-Ring section.  I have not been able to readily find the newer type nylon housing for this model as used on most of the later motors so I am not sure that they even exist.

Any person familiar with normal outboard repairs should be able to replace one of these impellers in 15 minutes.  The Clymer flat rate manual says it should take 1.3 hours.

A water pump housing assembly that has had a new style Nylon pump kit installed on a 4 bolt lower unit.  Impeller

It is recommended you replace the water pump to outlet tube grommet as well.   This grommet is held in place by 2 "ears" on the sides that snap into matching holes in the top of the water pump outlet tube.

Many times the grommet has been known to not slide over the tube properly, therefore giving a chance to allow the outlet water from the water pump to leak somewhat.  So it is beneficial to grease the lower end of the tube to help it slide in better.

Shown below is the water pump grommet, note the "ears"

Water Intake :  These motors main water supply to the water pump comes from a screened tube right behind the prop in the exhaust outlet.  Water is forced into the screened intake to the water pump by the prop thrust.  Some users report that when running these motors in a barrel, (usually a small one) that the prop has to be installed and usually in gear as apparently they need to get more water pushed to the water pump by the prop to get enough to cool when running  at over an idle.

There is a also a stainless steel intake plate with a few holes near the water pump area on the left side above the cavitation plate shown in the photos below.   Flush kits for this motor are rather scarce.  There is really no provision currently available for a easy muff system to run this motor out of a tank.  But there is hope. 

Aftermarket Water Flushing Adapter Cover :  These motors main water supply to the water pump comes from a screened tube right behind the prop in the exhaust outlet which utilizes the thrust from the prop to push water up to the water pump.  This method of water intake does not allow the newer type of flushing muffs to be used.  Flush kits were made for a while for this motor but now are not currently made and are rather scarce.  But there is hope.

On the LH (port side) of the exhaust housing just above the anti-cavitation plate there thin stainless steel plate (the factory nomenclature is water bypass cover) which is held in by 2 screws.  In this plate are 4 small clamshell type scoops that is designed to put water into the water pump when the motor is in reverse, as shown in the photo on the left below.  This is common to many different size of these motors up to 10hp in these years up to about 1974.  It was designed to supply water to the water pump when the motor was in reverse, however some motor owners think it is there for added water intake during forward running so you may see them in stalled either way.   

I have since talked to a old time marine mechanic about the direction of those holes.  Either he did not understand what I was saying or since his son took over the business and he has been out for a number of years, he forgot or did not pay any attention at the time.  After looking at as many as I can come onto, I now have concluded that the scoops probably were originally installed forward.  A few of these have this plates were painted over originally and little evidence that it had ever been off, as seen in the LH photo below.  Plus if you look at a factory exposed drawing, these arrear to be on the forward end.

AND thinking about it, this would supplement a partially plugged intake screen behind the prop, which seems common with these motors.

The thought of them facing rearward IF they are indeed a reverse intake, sounds plausible, however when in reverse, you would at minimal speed and will not be doing this for a extended period of time, so possibly either way would suffice. 

The right photo below is from a 10hp is an commercial aftermarket adapter (no longer available) with a 3/8" course thread placed inward in the rearward part.  This allows the usage of Mercury's Quick-Silver Flushing Device described below.  This flush plate apparently was NOT designed to be used when running, only for flushing, however this motor was a running motor, with no evidence of failure.   Since these are no longer made, you can fashion one by using the original plate as a sample and soldering/brazing, (even epoxy) a 3/8" course nut onto the outside of it to screw the flushing adapter into.  Or if your intention is to leave it in place and run the motor that way, I would solder the nut on the inside to give less resistance and less chance of debris hanging up on anything exposed.

 Evinrude with original reverse water inlet plate Johnson with aftermarket flush plate

Mercury sells a flushing adapter that uses a 3/8" National Course bolt thread on one end and a female garden hose end on the other.   Mercury's Quick-Silver part number is  #24789A 1 with the actual name being Flushing Device.  Also OMC Johnson/Evinrude uses the same adapter to back-flush their 9.9/15hp 2 stroke outboard motors (and maybe more models) made from 1993 to 2007.   These adapters also fit about all of the Japanese outboards that use a back-flush system.

You can remove the 3/8" plug bolt, screw the garden hose into the adapter, then into the motor, then turn on the water.  It does not need to be full force of the standard house water pressure, but about 1/2 force.   Start the motor up and let it run for long enough to get the motor warm enough to open the thermostat allowing water to flush thru the power-head.  

Mercury Outboard Flush Device  #24789A 1

The lower unit gearbox is not the unitized type as used on the later 9.9s but has a bottom section that when the unit is turned upside down, exposes all the gears and output shaft.  There is a spaghetti type O-Ring that seals the grease in the lower unit when assembled.

Prop In the early/mid 1970s OMC offered a accessory Lexan prop for the 9.5 hp.   That is all they offered for a short time was the replacement 3-blade, 8 1/8 diameter, 8" pitch prop (part # 385940) but later they dropped them and reverted back to the aluminum props.  That same prop was also spec'd as the replacement prop for 1958 - 63 10 hp motors.

The prop is secured by the old standard style using a cotter pin thru a plastic nose cone.  It is a 3 blade aluminum secured to the prop shaft by a 3/16" dia. by 1 5/16" long shear pin.   The prop overall diameter is about 8 1/2" dia. & has a 9/16" hub hole.

Prop & nose cone with cotter pin inserted. Lower unit showing drain & fill plugs

The motor that I worked on had a distance between the transom clamp area (where the top of the boat transom would be) to the cavitation plate of 18".   The owner thought it was a "Long Shaft", but upon measuring from the clamping area which would be the transom to the center of the prop it was 22", the same as most all later short-shaft motors.    The difference was really that the prop was a smaller diameter with the cavitation plate closer to the prop.  I also suspect that this was common before the later motors labeled "Short Shaft" became standard at 15" to the cavitation plate.

 

Copyright 2009 - 2014 LeeRoy Wisner  All Rights Reserve

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Originated 8-02-09, Last updated 12-13-2014   *
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