Oil leaking from dipstick

[jheathco]

Recently pumped oil and put in 5 fresh quarts of 10W-40 after servicing a boat that hadn't been ran in a few years.

Ran well for the first few hours, then the problems started. Appears the oil is overflowing rather quickly (has moved above the FULL line) and an oil/gas mixture appears to be squirting out the top of the dipstick at higher RPMs. Not much stuttering, but the engine is doesn't last long at idle RPMs before dying out.

Not sure what to check at this point. I initially thought I may need a carb-rebuild after noticing the oil case filling with what seems like gasoline (definitely not water), but after seeing some squirt out the top of the dipstick I'm starting to worry quite a bit more.

Could a bad carb be causing this? This is an old 5.7 Mercruiser.

 

[Bt Doctur]

Re: Oil leaking from dipstick

A bad mech fuel pump can dump fuel in the crankcase along with the carb floats dripping.

 

[HT32BSX115]

Re: Oil leaking from dipstick

A bad mech fuel pump can dump fuel in the crankcase along with the carb floats dripping.

I would agree that's a good place to start.

This is an old 5.7 Mercruiser.

DO NOT use 10W40 in any Mercruiser. Just follow the Mercruiser recommendations


Regards,


Rick

 

[jheathco]

Re: Oil leaking from dipstick

I'll have it the pump checked out... any other thoughts? Think a gasket could be the culprit, or the type of oil (although I doubt the type of oil would cause this)?

 

[backyard mechanic]

Re: Oil leaking from dipstick

Oil leaking from a dipstick is one thing. Spewing from the tube is another. If truly spewing, spirting or spitting oil under pressure from the dipstick tube is usually indicative of high crankcase pressure. Could be:

too much oil in the crankcase (find/fix/eliminate cause)
compression blow by (check compression)
PCV (positive crankcase ventilation valve) plugged (replace it)
blocked or resticted exhaust (check your exhaust bellows)
high/over rev of engine RPM (check prop/valves/timing)

 

[HT32BSX115]

Re: Oil leaking from dipstick

I'll have it the pump checked out... any other thoughts? Think a gasket could be the culprit, or the type of oil (although I doubt the type of oil would cause this)?

The oil has nothing to do with this. (You just shouldn't use that type of oil in ANY marine engine)

Your fuel pump has (or should have) a small clear hose that runs from the pump to the carb. That hose will have evidence of liquid in it when the diaphragm begins to leak. If the pump is mounted on the engine block, it may also allow fuel to be pumped into the oil sump diluting it and raising the level.

You need to ensure that the fuel pump is not leaking oil into the sump.

If it was via the carb exclusively the engine would not run very well. You'd also probably have a lot of black smoke from the excessively rich mixture.....It would be like a stuck choke etc or float valve stuck open.

 

[grahamh]

Re: Oil leaking from dipstick

I would check the PCV system.

 

[jtybt]

Re: Oil leaking from dipstick

If it is gas in the oil and it did this during a single run, I would suspect the fuel pump, pumping directly into the block. I've never actually run into this particular problem but nothing else fits the amount of gas you claim to be getting into your oil. A marine pump is vented back to the carb,as stated, and a bad diaphram will pump gas into the carb instead of leaking to the atmosphere...and it won't run right.

 

[jerryjerry05]

Re: Oil leaking from dipstick

Most boats don't have a PCV valve.Sounds like a fuel pump prob.If it's filling with gas and it's not filling from the carb then the pump is the culprit.
Do a compressiopn test too.J

 

[Haut Medoc]

Re: Oil leaking from dipstick

No old Merc has a PCV.....
I agree with the bad fuel pump...
Use straight 30 weight, or Merc 25w-40.....
I would drain the oil, & look for any signs of water as well....

 

[jheathco]

Re: Oil leaking from dipstick

Thanks guys. I'll let my mechanic know your collective thoughts and give you an update.

 

[Don S]

Re: Oil leaking from dipstick

The carb is not going to cause the oil level to rise like that.
The carb can only leak what is in the bowl into the intake manifold, then it has to get deep enough in the manifold to let fuel into the cylinder that has the valve open. Then it has to leak past the rings.
With the engine running, gas will never make it to the oil. All a leaky carb would do is make it run rich and flood out if it was really leaking.

 

[jheathco]

Re: Oil leaking from dipstick

Hey guys,

Just got the boat out of the water after a long day out in the ocean - ran pretty well!

Had the fuel pump replaced (the old one's diaphram was fairly corroded) and did a carb-rebuild. Thanks for the help with this.

On an unrelated note, my transitions from neutral into reverse aren't very smooth. Most times I have to move the throttle in reverse past the point where it clicks in before I can throttle back and settle it in - if I don't, I get a clicking noise as if it's trying to shift into gear but won't. Neutral to forward is fine, and both forward and reverse back into neutral are fine as well.

 

[TowRoper]

Re: Oil leaking from dipstick

start a new thread so everyone wont get confused on what help is needed OK
and congrats on fixing the fist prob!