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1986 40hp Johnson

S

steveragan

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" Last winter I purchased a ba

" Last winter I purchased a bass boat with a 40 HP Johnson outboard on it. This summer I was able to take it out a few times, the last time was approximately 3 weeks ago. The day after parking the boat in my garage I noticed that it had developed an oil leak dripping from the prop exhaust area. I know that with normal running it will get an oil residue in that area but this is substantially worse. Overnight in about a 12 hour period I had a spot of oil that was about 5 - 6" in diameter. I cleaned it up and over the next couple of days it reappeared twice. My motor is a 1986 40 hp. Johnson W/ oil injection from a an oil tank that sits next to the feul tanks. Can you help me figure out what can be wrong with it? I don't want to use it anymore till I get it fixed for fear of doing permanent damage. The motor runs great and that is the first time this has happened. Any help would be greatly appreciated! Steve Ragan "
 
"Steve.... OMC made two 40hp m

"Steve.... OMC made two 40hp models that year. I'm assuming that yours is the thru prop exhaust model.

If that oil that you see is pitch black, it is in all probability a excessive mixture of gas & oil draining down through the exhaust housing (the long housing between the powerhead and the lower unit) which would have its interior coated with pure black carbon deposits, much of which might be a fluffy type carbon.

This excess is usually caused by using 6 gallon portable tanks, having the vents closed, pressure building up within the tanks which in turn force fuel into the engine via a faulty carburetor assy, fuel pump diaphram, etc (It happens).

To tell for sure, do this. Locate the lower unit drain screw at the extreme bottom (skeg) of the lower unit which will be a large, regular slotted screw, and loosen it to a point whereas a small amount of gear lube escapes. If the lube is not black, but rather a normal oil color, then obviously the lower unit is not leaking.

However, to be absolutely sure, remove the top fill screw that is an exact copy of the drain screw, then fill the unit from the bottom dain screw until the lube runs out that top fill screw. The quanity used to fill the unit will tell the tale.

Note that on the 40hp commercial model, the exhaust does not exit through the prop, and this model has a philips screw in the lower unit that is actually a long shoulder type screw which acts as a pivot point for the internal shift linkage. For those who have this type lower unit DO NOT remove that philips screw unless you're in the process of dismantling the lower unit.

Joe
"
 
"Thanks Joe,
I did the ch

"Thanks Joe,
I did the checks on the lower unit fluid that you suggested and everything was Okay there oil was correct color and fluid level was same as when I changed it this spring.
If it is the carburator assembly, or fuel pump diaphram how much do you guess that it will cost to get fixed?"
 
"Steve.... Have the engine in

"Steve.... Have the engine in a upright normal running position, and if the carburetor has a covered faceplate, remove the cover so that you can see the carburetor throat(s). Now, pump the fuel primer bulb up so that it's hard. If fuel flows out of the carburetor throat(s), they'll require rebuilding. If no fuel flows out of the carbs, they're okay.

Carb kits are about $18.00 and rebuilding the carbs, if dual carbs, would be about three hours labor which includes test run and adjustments.

Pertaining to the fuel pump... if the pump or VRO has a seperate line that operates the pump, remove it from the block or wherever. If the pump diaphram is faulty, fuel will flow out of that line from the fuel pump when you pump the fuel primer bulb up hard.

If the pump is the type that has a gasket in back of it and operates directly off the block, remove the two long screws that attach it to the block then put nuts on those screws to hold the pump tightly together, then pump the fuel primer bulb. If that type pump has a faulty diaphram, fuel will flow out that back pressure hole that was against the gasket.

If no fuel leakage is present, I'd assume that the carb(s) and fuel pump are okay. Crack the caps or vents on the fuel tanks if they're building up pressure.

Joe
"
 
" Joe,
I was checking my

" Joe,
I was checking my carbs. and fuel pump as you suggested I removed the air intake cover. When I pumped up the primer bulb I noticed a lot of fuel coming out of what I think is the fuel pump.
It is attached to the back of the the air intake manifold. there are three hoses attached to it two on bottom and one on top. The top hose loops down to the side where it splits down into three smaller hoses. If this is the fuel pump what do I have to do to get it fixed rebuild or replace?
I really appreciate you help and advice on this since I really don't know anything about boat motors. "
 
"Steve.... You have described

"Steve.... You have described a leaking VRO fuel/oil pump. I'm assuming that all of the lines are attached, and that the fuel leak is actually exiting the pump elsewhere? If so, you have a faulty VRO pump and it will require replacing or rebuilding if a kit is available for it.

That VRO pump is expensive $250/$300 range, and since it is a plastic like material, an inexperienced person could easily break a fitting. Something to keep in mind.

Look the VRO pump over closely befor you make the purchase as the leak may simply be due to a loose or broken clamp on one of the hoses.

Joe
"
 
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