Merc 454 Alpha​ catastrophic failure - I have a few questions

[CaptRonn]

It makes me wonder if the engine was rebuilt as the seller claimed.
.

In aviation we call it a Krylon overhaul.

Personally I don't buy shade tree overhauled anything. If someone sells me something advertised as rebuilt, overhauled, whatever, I want it to come from a reputable shop.

 

[bergs]

These things happen so don't be too hard on yourself.

I am curious because you mentioned that the Seller rebuilt the engine "last year". No one I know puts an old fuel pump back on a rebuilt engine. Even the cheap rebuilds get a new fuel pump because they always fail with age (although the vast majority fail due to ruptured diaphragms). I just raise the point because we just don't see a "fuel pump fail and flood the block" problem happen on CSR. In fact, in 10 years on this Board I have only heard of this happening one other time. It makes me wonder if the engine was rebuilt as the seller claimed.

It's unfortunate but you can take the steps now to ensure it never happens again.

Since pulling the engine and looking things over, I too have my doubts about a rebuild ever taking place. Maybe the seller misspoke or I misheard but I absolutely do not believe this engine was rebuilt. There are simply no indications this engine was taken apart at any time.

Also, I can confirm 100% that the fuel pump was not the source of the issue and in fact this engine pulled water into the crankcase. It did not hydrolock but I definitely jumped the gun with my stating it was a fuel pump failure and for that, I apologize. I based my statements off the limited information I had at the time of my posting.

I will certainly be taking the time to locate the source of this failure as I am not accustomed to blowing up engines and this one was completely unexpected.

 

[aerobat77]

it gets strange ... you stated the oil was not milky and with that amount of water inside it will be milky for sure.

 

[bergs]

I agree and have not gotten to a place where I understand the observations I made the day after the engine blew.

The oil on the dipstick did not appear to be milky and it looked like the engine was overfilled with oil. A friend of mine was a witness to this.

When we pulled the engine, there was a small spill from the hole in the oil pan and the oil/water mix was milky without a doubt.

I suppose the question is, is it possible for any amount of oil to separate even after it's been churned up with water?

 

[scoflaw]

It will be milky when you drain it. This will cost several boat bucks, feelin your pain

Seen it before....clean oil on top, depth of dipstick, milk on the bottom

 

[bergs]

To close this out for any future readers: Issue has been traced to an aft portside head gasket failure.



Again, my apologies for jumping the gun with saying it was a fuel pump.

 

[wetcoaster]

I'm looking to swap my engine from my Mercruiser MCM 7.4L with 30 hours on the rebuild to a 6.0LSX if you're interested in a direct replacement. I could have the engine out and shipped in about 2 weeks.