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5.7 L 1997, 450 running hours, now an Oil Leak

E

EuroDriver

New member
I have had the boat since new, with next to no problems

After the winter overhaul by the boat yard, the bilge was clean as a kitchen floor. Now after 4 running hours the bilge is has a lot of engine oil, and sump has probably lost about a quart of oil.

When engine is running, oil pressure is normal

I checked around the oil filter cartridge and the pipes leading in and out of the filter holder, it seems to be tight.

What things should I check ?

Engine is fitted to a Bravo 3 sterndrive
 
Welcome aboard !

The pan lip ?

The pan drain ?

The oil sender ?

You have 2 o-rings on the filter the old one and then when changed the new one.

valve cover.

You see no oil on the motor itself ?
 
The oil in the bilge is coming from the oil pan. The pan has rust blisters surrounding the drain plug, and the blisters are wet with oil. As the engine oil warms up the leaking rate increases. I have put a plastic container under the oil pan to catch the leaking oil, so as to keep the bilges clean.

Hopefully the leaking rate will stay manageable for the next 5 weeks !
 
Is it really leaking from around the drain plug? I would bet that it is not, and it's dripping from there since that's the lowest part of the engine. Oil typically tends to cling to things until there's nothing left to cling to. (Kind of like finding a small leak in a leaky roof... it goes all over the place until you see a spot in the ceiling as far away from the point of origin as possible!)

What I've found with these engines as they start to wear, the crankcase vent system is woefully inadequate. Piston blow-by pressurizes the crankcase and oil starts to leak out of the front and rear main seals.
In lieu of an engine rebuild, make sure your crankcase vent lines are clear, and make sure they are as close to the flame arrestor as you can get them.
I actually drilled a hole in the top of my flame arrestor and put a tee fitting through the top and connected the crankcase vent lines (through suitable PCV's, obtainable at just about any car prats store) to the tee fitting. Once that was done, no more oil leaks.
Keep in mind, a PCV (crankcase vent valve) is crucial to prevent a backfire through the carb from igniting crankcase gasses and causing an explosion!
 
troym said:
Is it really leaking from around the drain plug? I would bet that it is not, and it's dripping from there since that's the lowest part of the engine. Oil typically tends to cling to things until there's nothing left to cling to. (Kind of like finding a small leak in a leaky roof... it goes all over the place until you see a spot in the ceiling as far away from the point of origin as possible!)

What I've found with these engines as they start to wear, the crankcase vent system is woefully inadequate. Piston blow-by pressurizes the crankcase and oil starts to leak out of the front and rear main seals.
In lieu of an engine rebuild, make sure your crankcase vent lines are clear, and make sure they are as close to the flame arrestor as you can get them.
I actually drilled a hole in the top of my flame arrestor and put a tee fitting through the top and connected the crankcase vent lines (through suitable PCV's, obtainable at just about any car prats store) to the tee fitting. Once that was done, no more oil leaks.
Keep in mind, a PCV (crankcase vent valve) is crucial to prevent a backfire through the carb from igniting crankcase gasses and causing an explosion!
Click to expand...

We were suspicious about the possibility of piston blow by causing high pressure in the sump, but the oil pan has such large blisters of rust which are wet with oil, that we are pretty sure that the pan is somewhat porus. What I will do is to have the PCV changed out tis winter
 
What i find is when the pan starts to drip it' gets worse fast.

And when you do pull the motor and look at the pan held up to the sun you might see pin holes.

And then you got to look at everything.

And after you are done and ready to install it paint the whole motor 4-5 times and the bottom you won't see agiain till
the motor comes out again.

You will also get thechance to inspect the bilge area and the bottom corner of the transom.

Good luck !
 
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