Mercruiser 4.3 with oil leak

[Snowmeltriver]

First, thanks for all the thoughtful responses on this forum. I have already learned a lot.

Last spring we bought a 2003 Bayliner with a 4.3 Mercruiser engine. It's been a perfect family boat.

At the end of last season, I found a minor oil leak from front of block when warmed up. I've cleaned everything, run it on earmuffs, and isolated the leak with a mirror. I'm pretty sure its the front crank seal as that seems like a common thing. There is just a drip from the front edge of the oil pan that looks like every other photograph that people have posted with this issue. There is no circular spray pattern from oil weeping through the keyway and spinning off the harmonic balancer or crank pulley.

1) I wanted to check the PCV valve first (before swapping the crank seal) as I read that that can increase crankcase pressure and push oil out strange places. Funny thing is that neither valve cover has a pcv valve, both are just 90 degree elbows to route the vent hoses to the spark arrestor. The Mercruiser parts diagram definitely shows a pvc valve on the port side. Do I need a PCV valve? Could this be related to the oil leak?

2) How much fuel smell is normal when opening the engine hatch? I assume some gas smell is normal since its a carbureted engine.

Thanks! That's it for now.

 

[achris]

Hello Snowmeltriver and :welcome: to iboats.

If you can post your engine serial number whenever you start a new thread, that would be great.

It's likely your oil leak is a distorted oil pan pushing on, and then cracking the composite timing cover. A known issue with the V6s of that era. The only fix is to pull the engine and put a new timing cover and oil pan on.

No PCV valve on those engines. Which parts diagram are you looking at?

If you can smell fuel, find the leak and fix it.

Chris...

 

[Rick Stephens]

Shouldn't smell gas. Boats make good bombs since the vapors don't have anywhere to go.

 

[Scott Danforth]

Hey achris , you may want to post a link to your oil leak woes....

 

[achris]

Hey achris , you may want to post a link to your oil leak woes....

Not really. It'll just make me start crying all over again.

https://forums.iboats.com/forum/engi...pdate?t=373060

https://forums.iboats.com/forum/engi...oil-leak-fixed

https://forums.iboats.com/forum/engi...-bilge-finally

Chris.....

 

[nola mike]

Did you ever find out what years were affected? From your and other posts it looked like they were later 4.3s, whereas they started with the plastic in '96 or so... And I never saw if it was determined that it hit gm car engines as well?

 

[Lou C]

It seemed to be a narrow range of years, not all with the newer design were affected. Ironically leaks there can happen on all variants of the Chevy small block V6 or V8 but never had a leak there on my old '88. Just the natural seepage you would expect on an old engine. Maybe the old tin covers were better who knows.

 

[Snowmeltriver]

Hello Snowmeltriver and :welcome: to iboats.

If you can post your engine serial number whenever you start a new thread, that would be great.

It's likely your oil leak is a distorted oil pan pushing on, and then cracking the composite timing cover. A known issue with the V6s of that era. The only fix is to pull the engine and put a new timing cover and oil pan on.

No PCV valve on those engines. Which parts diagram are you looking at?

If you can smell fuel, find the leak and fix it.

Chris...

Engine serial number is 0M648222, Family 3M9Xm04.32VC, DOM April 2003

I hope it not the oil pan. I'm going to try the crank seal first.

Really, no fuel smell at all? That's concerning. Any ideas where to start that hunt?

Thanks,

 

[Snowmeltriver]

Not really. It'll just make me start crying all over again.

https://forums.iboats.com/forum/engi...pdate?t=373060

https://forums.iboats.com/forum/engi...oil-leak-fixed

https://forums.iboats.com/forum/engi...-bilge-finally

Chris.....

Wow. That was a saga and I'm so sorry that you had to deal with that. I am mechanically inclined but I'm not about to pull the engine myself...way over my head.

In one of your threads, you say "It also looks like it was only one mould, and only for the very later 2005 and the 2006 V6s... Looks like QA/QC got to it, but not before quite a few engine went out..." My engine is a 2003 so it's unlikely that I have the poor casting issue that you were cursed with. Correct?

 

[achris]

Wow. That was a saga and I'm so sorry that you had to deal with that. I am mechanically inclined but I'm not about to pull the engine myself...way over my head.

In one of your threads, you say "It also looks like it was only one mold, and only for the very later 2005 and the 2006 V6s... Looks like QA/QC got to it, but not before quite a few engine went out..." My engine is a 2003 so it's unlikely that I have the poor casting issue that you were cursed with. Correct?

Yeah, that might have been premature. I have since heard of the problem on some later engines. It maybe that some of the bad sumps got through and weren't used until much later.

If you have a bad sump, at least you know what needs to be done. The trail has been blazed, as it were.

BTW, pulling the engine from a boat is plenty easier than a car. Usually about 2 to 3 hours work. Pull the drive first. (see my videos for that. Link at the bottom of my signature)

Chris.........