Poker Run = massive oil leak

[jumpjets]

I ran my little100% stock Rinker 262 family boat in a Poker Run yesterday against some serious race boats. My mercruiser 2007 6.2L EFI engine was at 4800+ rpm for almost 2 hours straight. It’s rev limited at 5200 rpm. I fully acknowledge that this was stupid and I had no business running the boat that hard.

I started the the day with a full oil pan, and no oil leaks. After absolutely flogging the engine, it’s now 1 quart low. All the leaked oil is very clearly in the bilge.

Before I start tearing apart the engine bay looking for the leak, are there any common places I should look? Does the merc 6.2L have a notoriously weak rear main seal or anything like that?

 

[achris]

That 6.2 is just the same as the 305 and the 350. So, any 'weak areas' will be the same.

Have you run your hand along the bottom of the sump (oil pan) to see if it's 'wet'? If it is, you have a place to start tracking back. See where that oil is coming from.

Chris.......

 

[Grub54891]

Clean the entire engine, and bilge areas fully. Spotless clean. Lay white oil sorbs down, run it and keep looking for any drips, or leaks. Front seal, rear seal, valve covers, intake ends, even the dipstick where it goes into the block, oil sender also. Good luck!

 

[achris]

Clean the entire engine, and bilge areas fully. Spotless clean....

For most boats I see, that's a weeks work right there....

Chris......

 

[jakwi]

I had something similar happen not to long ago. Make sure you have oil in it, then start it up and get down there with a flashlight and look for a drip.

For me one of the oil lines that feeds the remote oil filter had been rubbing on the engine mount, and after 10 years it had rubbed through. Given that you were only 1qt low, and not empty, I'd put my money on a steady drip, rather than a giant hole.

Good Luck!

 

[Grub54891]

For most boats I see, that's a weeks work right there....

Chris......

Well yes it is. But if you get it clean, it's easier to maintain in the future, you get all the loose bolts, screws, clamps, fishing line, and pullties junk out of there that can jam up that bilge pump.

 

[Scott Danforth]

You should be able to run 4800 rpms for hours, however Mercruiser does state up to 1/2 qt per hour of burn is normal :/

My guess is a bit of blow by. Was there oil on the valve covers?

Clean bilge and check

If you have no leaks, top off the oil and go boating

 

[Scott06]

You should be able to run 4800 rpms for hours, however Mercruiser does state up to 1/2 qt per hour of burn is normal :/

My guess is a bit of blow by. Was there oil on the valve covers?

Clean bilge and check

If you have no leaks, top off the oil and go boating

i loose some oil when hitting it hard for extended time. You get aeration and windage off the crank plus any gas or moisture in oil gets burnt off running that long at WOT. I'd fill it and watch. Did the oil pressure stay up during that long run? Above 45 psi ?

When you say clearly in the bilge you have a quart of oil in there? Likely blow by as stated above and should be visible on outside of engine top

No issue runing wot fir extended periods of time. Done it on every boat I've owned and they hold up just fine.

 

[jumpjets]

Update:

after letting the boat sit sit for a few days, it looks like I only lost about half a quart, maybe less.
It looks like there is more oil in the bilge than there actually is, since it’s sitting on top of some water.
I felt all around the main seals, head gaskets, valve covers and oil pan for a leak. The engine exterior is dry. I still want to inspect the remote oil filter assembly and plumbing. It very well might just be some blow by.

I guess ive been babying my engine. I didn’t realize other folks ran them that hard.

 

[Scott Danforth]

i loose some oil when hitting it hard for extended time. You get aeration and windage off the crank plus any gas or moisture in oil gets burnt off running that long at WOT. I'd fill it and watch. Did the oil pressure stay up during that long run? Above 45 psi ?

just like most street rods I built..... marine motors really need a catch tank breather setup.

 

[jumpjets]

Ok I examined every inch of the engine and I can’t find a leak. The engine is bone dry. The air cleaner nasty with oil where the Breather vents into it. I think there was hi blowby at hi rpm like you guys said. I’m gonna cleanup the mess and call it good.

Next question: my outdrive oil resiviour is way low. I pulled the upper & lower Bravo III oil fill screws, and the drive seems fine. Where did the drive oil go??

 

[Grub54891]

Next question: my outdrive oil resiviour is way low. I pulled the upper & lower Bravo III oil fill screws, and the drive seems fine. Where did the drive oil go??

Are you sure its motor oil in the bilge? It could be drive oil from a leaking line. ​

 

[jumpjets]

I suppose it could be drive oil. I’ll check the viscosity & inspect for a leaking line.

 

[jumpjets]

Hey guys, update on my drive oil leak:

I determined the leak was a faulty wire in the drive oil reservoir. I replaced the plastic reservoir and it sat in my driveway leak free for 6 weeks. I also drained all the drive oil and refilled the drive, using a pump to fill it from the bottom up.

I ran the boat one final time yesterday. After the 2 hour run, the brand new reservoir was 90% empty and the alarm was sounding!!! The reservoir cap was wet with oil, and there was oil all around the bilge. It seems like it gushed out of the overflow valve on the cap?
What the heck happened? Did the new oil expand under heat and blow out of the cap? Did I fill the drive wrong? Did I overfill it? Underfill it?

 

[Scott Danforth]

or the plastic fitting at the transom shield is broken