Fuel Leak from Crankshaft Bearing Cap

dblanton

Petty Officer 2nd Class
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Sep 22, 2006
Messages
101
On an 81 75hp Evinrude I have fuel dripping from the lower crankshaft bearing cap when I kill the engine, is it supposed to do that as some kind of way to drain excess fuel from the crankcase when the engine is not running? Doesn’t seem to be a problem while the engine is running.
I have checked all the fuel lines, carb's, intake gaskets etc but no sign of a leak. Engine runs great at idle and at WOT. The fuel drips from the bolt heads that attach the crankshaft bearing cap to the block. I replaced the seal and the o-ring on the crankshaft head assembly but that did not fix it and no sign of fuel leaking from top side and running down.

As a test I cleaned all the leaking fuel so everything would be dry and clean; then I connected the fuel line and gave the bulb a few good pumps to fill the carb's with fuel and just let it set to see if fuel would leak. No sign of a leak after sitting for 1 hour with pressure on the primer bulb, then I turned the engine several times by hand and let it sit another 1 hour still no leaks. After that I started it up with the ear muffs on and let it idle for three minutes then shut it down and watched for a leak, within a few seconds fuel began leaking from around the flange of the crankshaft bearing cap. I have isolated where the leak is coming from but I don't have any idea as to how to fix it. Again I have already replaced the seal and the o-ring on the crankshaft bearing cap in an effort to correct the leak. Any advice and help would be greatly appreciated.
 

Robert16star

Cadet
Joined
May 13, 2007
Messages
14
Re: Fuel Leak from Crankshaft Bearing Cap

""As a test I cleaned all the leaking fuel so everything would be dry and clean;""

Sorry I have no help for your issue, but I do have a question. What did you use to clean the engine?
 

Joe Reeves

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Feb 24, 2002
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Re: Fuel Leak from Crankshaft Bearing Cap

As pictured below, the lower main bearing crankshaft cap is retained to the bottom of the powerhead with four (4) bolts, and the powerhead is bolted to the adapter plate and main exhaust housing assembly, hidden from view.

Yet, you state that you run the engine and then wait and view this retaining cap to observe the leak you speak of.

Apparently I'm missing something here. I'd appreciate having you elaborate on this somewhat to clear up my confusion.

81_75hp_CS-2.jpg
 

dblanton

Petty Officer 2nd Class
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Sep 22, 2006
Messages
101
Re: Fuel Leak from Crankshaft Bearing Cap

The fuel is seeping from around the flange of the Crankcase Head Assy. (# 20 on the parts diagram) and drips off of the bolt heads that attach the Crankcase Head Assy. to the engine. I have replaced the seal (#21 on the parts diagram) and the O-Ring (#19 on the parts diagram) in an effort to resolve the fuel leak issue but to no avail. I would estimate that there is approximately an ounce of fuel that leaks out when the engine is shut down after it has been running on the ear muffs for 5 minuets or so. Some fuel leaks while the engine is running on the muffs but not as much as when the engine is shut down. I have very thoroughly examined all the fuel lines, carb's and gaskets etc thinking the fuel was coming form another area but the fuel is defiantly seeping from around the flange of the Crankcase Head Assy.
 

Joe Reeves

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Re: Fuel Leak from Crankshaft Bearing Cap

If that lower crankcase assembly O Ring and seal is seating properly and I believe you've made sure of that, the only way the fuel/oil mixture could gain access to that area from the crankcase (in my opinion) would be that the crankcase halves (front to rear portion) are not sealed properly with GelSeal.

Also, if the powerhead to adapter plate gasket was faulty (or either sealing surface pertaing to it), the unburnt fuel/oil mixture could be blown towards that crankcase seal assembly..... in effect making it look like that assembly was leaking.
 

dblanton

Petty Officer 2nd Class
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Sep 22, 2006
Messages
101
Re: Fuel Leak from Crankshaft Bearing Cap

I have replaced the gasket that goes on top of the adaptor plate (#30) on the attached parts diagram but not the one that goes on the bottom of the adaptor plate (#25) on the attached parts diagram. Would either of these gaskets if bad have the same effect that you mentioned before?
Is there any possibility that the fuel pump has anything to do with the leak?
 

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Joe Reeves

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Re: Fuel Leak from Crankshaft Bearing Cap

Only gasket #30 or either surface it seals to if faulty would result in that problem.
 

dblanton

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Sep 22, 2006
Messages
101
Re: Fuel Leak from Crankshaft Bearing Cap

I replaced that gasket when I replaced the seal and O-Ring.
My manual did not give specific instructions as to the orientation of the seal, that is, which side of the seal would be facing the bottom of the crankcase or which side of the seal would be facing the exhaust tube when the bearing cap is installed. I did however install the new seal facing the same way as the old seal was installed, and that was the hard side (wider metal side) of the seal facing the bottom of the crankcase when the bearing cup is installed. Is this the correct position of the seal?
 

Joe Reeves

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Re: Fuel Leak from Crankshaft Bearing Cap

Yes, That's the correct installation procedure.
 

dblanton

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Sep 22, 2006
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101
Re: Fuel Leak from Crankshaft Bearing Cap

Still no luck fixing the leak; someone locally said that the #3 carb could be flooding a little and allowing fuel to collect in the reed box and is draining down, is that a possibility? Also I assume that the O-Ring is supposed to seal the bearing cap to the two crankcase halves and that is why there is no gasket on the flange of the bearing cap. If so would it hurt anything to put some sealer on the O-Ring when installing the bearing cap to the crankcase, and make a gasket for the flange of the bearing cap.
 

Joe Reeves

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Re: Fuel Leak from Crankshaft Bearing Cap

If the crankcase was sealed properly, you could remove the carburetor and intake manifold, and then pour in a quart of fuel mixture in that lower crankcase area...... and nothing would be leaking out at the area you mention.

If you're unsure that the base gasket (PH to Adapter Plate) or the two sealing surfaces aren't flawed, you could double gasket that area and use Gasket Sealer (worked in the past). You can also use Boat Armor Sealer 1000 or OMC Adhesive (Whatever Bombardier calls it now) on that "O" Ring.

Frankly, if that doesn't do it, I'd tear the engine down and then clean reseal the crankcase halves with GelSeal.
 

dblanton

Petty Officer 2nd Class
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Sep 22, 2006
Messages
101
Re: Fuel Leak from Crankshaft Bearing Cap

Since I have the Power head off I am going to reseal the crankcase halves like Joe suggested, but before I do I have a question.
I am ready to separate the two halves but before I remove the bolts to separate the halves I was curious if the power head had to be in any certain position, I have the power head sitting on my work bench in the same position as it would be when it is mounted to the leg on the boat, is it ok to separate the halves in this position? I know to some this may sound like a stupid question but I just want to be sure that the crankshaft won't drop down or out pulling the pistons down to low.
My manual doesn?t say any thing about what position the power head should be in but it does give detailed instructions on how to separate the halves.
 
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