Mercruiser 7.4 MPI Water in Oil.....HELP!!

[Lucrative]

I've posted a video with the best description and video I could do. Sorry for the terrible camera/flashlight work, trying to coordinate too much and still explain what happened. Here's a quick history: Engine overheats after running at 3500 rpm for a few minutes (will cool down when run at idle). Engine had overheat/low oil/whatever else alarm go off, but temp gauge was failing too, jumping from no reading to 180-190, so I fixed the water temp gauge by replacing the sensor. Took it out again, sure enough, verified with new sensor it was overheating. Engine will run cool if it's below 2000rpm. I suspected the impeller, so I replaced that with a new sea water pump kit. I did find 2 fins broken off the impeller and found them in the oil cooler. Got all pieces out, thought if that didn't work, I'd be replacing manifolds and risers. Took the boat out again. Overheat again when run at 3000-3500rpm for a few minutes. On the way back in, I was idling, then tried to give it some power to see how it would act with the heat up/cool down and I heard a knocking noise. Located it on the port side engine in one of the rear cylinders. Checked the oil, and it was milky. I have checked the oil each time out, and this is the first time I had water in it. I thought blown head gasket, and have taken the engine down to the heads. When I pulled spark plugs they were oily and black and, water came out of the rear 2 cylinders, and both of those cylinders have some rust on them, but the front two and the starboard side seem to be only effected a little by the water in the oil. I couldn't find any area of the head that appeared to be blown out, and I'm trying my best to locate the source of the water. I'm very new to this and am pretty baffled at this point. After looking at the head gaskets, I went back to the port side exhaust manifold. Plugged it and filled with water, but it doesn't appear to be leaking. Not sure what to do or where to go from here. Am I missing something?

Here is a link to a YouTube video where I show as best I can the current state of parts. https://www.youtube.com/watch?v=3exq...ature=youtu.be

Any help is appreciated!

Thanks,

Luc

 

[tpenfield]

Do a leak test on the exhaust manifolds. Looks like you may be getting water accumulating at the rusty exhaust port during idling.

Too bad the engine is all apart, as you could do a compression test, etc.

Post engine serial number when you can.

 

[Bondo]

Ayuh,.... Welcome Aboard,...... Yer lookin' in all the wrong places in yer video,...

The Failure point of the manifolds/ risers, is the Gasket, 'n it's matin' surfaces,......

Take the gasket remnants off, 'n clean the gasket surfaces of the manifold, 'n riser with a flat file, keepin' the surfaces Flat, down to clean cast iron,.....

Then measure how much meat is left, 'tween the water passages, 'n the exhaust passages,......
If it's to spec, put new gaskets, in, 'n run 'em,....
If it's to narrow, buy new manifolds, 'n/ or risers,....

 

[Lucrative]

Hey, thanks for the replies. How am I going to measure the remaining cast iron on the exhaust manifold and risers? I've never done this before. Also, where would I find the specs for this? I will get the engine serial number in the morning and post it. Thanks again!

 

[Lucrative]

Also, Bondo, why do you think it's the gaskets between the risers/exhaust?

 

[NHGuy]

Cause when that gasket fails the cooling water gets in the exhaust manifold and breaks stuff. Common problem.

 

[Lucrative]

Thanks for the responses. Given the history of overheating issues, should i not also be replacing the risers and manifolds at this point?

 

[Lucrative]

Gentlemen, thanks again for the help. I was hoping to get some input on replacing the risers/manifolds, but I have gone ahead and ordered new ones anyways. I just really want to try my best to make sure when I get this sucker back together it's going to run well.

If you saw my video, you've seen that I have the engine stripped down to the block. I'm going to pick up my parts for the rebuild right now and hope to rebuild back up to the intake this weekend. This is my first time doing anything like this and I've consulted Youtube, but haven't found much in the way of instructional videos for this project.

Looking for any pointers and "don't F this part up" type of advise when I'm reassembling. Also, tried to find the torque specs and pattern for my head bolts. I'm pretty sure it's 85 ftlb, but can't locate the pattern.

For reference, my engine serial number is - 0L609594

Also, I cleared a bunch of junk out of the block. There was some sediment mixed with flakes of cast iron. I think this part is called the "water jacket", but like I said, I'm new to this. I did my best to scrape off any loose pieces, then blew it out with a hose, then sucked it all out with a wet/dry vac and repeated. At what point should I be concerned about the amount of material coming out of the block? I don't know much, but I do know if one of those cylinder walls cracks open and water flows into a cylinder I'm in for it.

 

[camalot]

Sounds like you may have two things going on, for the water in your oil "if it was winterized correctly " I would get the inlet manifold checked. A rusted out/cracked inlet manifold will let water into the engine and above the piston.

 

[Bondo]

How am I going to measure the remaining cast iron on the exhaust manifold and risers? I've never done this before. Also, where would I find the specs for this?

Ayuh,.... Follow the links found in Don'S Adults Only section at the top of the I/O forums,....

Links to factory manuals, with the torque specs too,...

Btw,.... The water jacket is not the places ya gotta get spotlessly Clean,.....

That's saved for gasket surfaces, 'n things where the oil is, 'n where the gas passes through,.....