Maintaining Johnson QD Series 10 hp 2 cycle outboards 1949 – 1963   (Information & normal repairs)

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

 

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 & condensers.  The tune-up kit (the whole set of 2 points & 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. 

 

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

Top of timing plate showing ignition system

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

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

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

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

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

The carburetor has 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.

In the photos below you can see the bottom or high speed jet & it's linkage to the control knob. The knob operating this jet slides over a octagon sleeve around the idle jet shaft.

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

There are other mounting that holds the lower upper cowling to the mid-section /clamping unit.  These tend to have the bonding from the bolts to the rubber deteriorate & 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.    So probably the best would be to try to clean them & then Super Glue.  The result is not detrimental to the running of the motor, except the upper cowling when snapped to the lower part has some movement & can make a rattling noise when running.

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 & 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.

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 & bottom.  Remove this cover & you can then get to the coupler & 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 & 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 & tighten down the screw.  The one I worked on had a tendency to slide up too far & could bind the screw when it was tightened, stripping the threads.  A flashlight & slow movement of the shift lever is needed in this situation.

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.  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.

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 the water pump & impeller at 1958 when the cowling was also changed.  The earlier impeller is the same as the 10, 15 & 18 hp of the same years.  And the 1958 & 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 & 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 & 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.
 

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.

This grommet has been improved in that by looking at the illustration below, the sides now have been made wider & taller.  This appears to be to elevate the problem of upon final assembly as you are trying to align this tube into the grommet & slide the lower unit upwards trying to align the driveshaft splines into the crankshaft, (all without much vision).   It is also best to lubricate the copper tube with some Vaseline for assembly so it slides into the grommet better.

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.  This can be checked by running the motor with muffs over the water intake, & watching at the upper part of the lower unit where the shifting rod goes up to the powerhead.  If water is being forced out around the shifting rod grommet, you can bet that the water pump grommet is not seated correctly.   This new grommet is designed to help eliminate this problem, so it is recommended that you replace it when replacing an impeller.

The grommet has been changed but they left the part number the same.  This same grommet is used for many different OMC models.

The water intake is in the leg protrusion behind the prop, being forced into a screened intake from the water pump by the prop thrust.  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 photo above.    I have made a new plate with a 3/8" nut silver-soldered in place to accommodate the later universal 3/8" screw in flush adapters that can be interchanged with this plate for flushing.  There is really no provision currently available for a easy muff system to run this motor out of a tank. 

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 & output shaft.  There is a spaghetti type O-Ring that seals the grease in the lower unit when assembled.

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.

 

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.

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

The twist grip & throttle uses cog gears similar to the earlier series motors.