Dock Holiday
 

New head, new block, 1 new piston, for sure. I will replace all pistons since we are opening the bottom end. I will know more once they get the bottom end torn down. Intake & exhaust vavles look great, all springs also look good but will be replaced. We are diffently going to do the gaskets and springs on the port motor just in case. I do not know if this is a common problem or what? But it might be worth it to pull the heads on your motor and check just for peace of mind. I know that I will be replacing head gaskets every 100 hours after this no matter what. I have been told that no test would have shown this problem, not sure it that is true or not. I know that the opposite side of the same motor showed the exact same wear to the gaskets, it just had not torn completely yet. That side compression tested at 145 to 150 on cold cylinders and was on its way to the same problem. My old HP500EFI's had 180 hours and I never one problem ever.

3DO

Insptech
 

They have eliminated detonation from the equation and are blaming it purely on the gasket. I can get pictures and will post them tommorow. I would love to get your opinion on this. We too have been thinking about the same thing, if there was detonation, what was the cause, lean running condition, bad fuel, clogged injectors, the list goes on and on.

The pictures will be up tommorow evening. Thanks

3DO (Jeff)

Jeff

Look at the thread "Broke a 575 SCi". That my motor and it show pictures of exactly what sounds like happened to your motor. The 575 is a 502 block and I'm sure uses the same head gaskets.The motor had about 120 hours on it. I was noticing loss of power for some time before it let go. I was planning to pull it apart in the winter but didn't make it that far.

My port side motor was on its way too. Both are being reworked with the Cometic gaskets. Everyone told me the Merc gaskets suck, except for Mercury. I heard the same crap from them. We do not cover head gaskets. I have extended warranties on the motors and guess what, they don't cover head gaskets either. They claimed bad gas which caused detonation. I don't think so.

Anyone that has these motors and are around 100 hours should replace there head gaskets. Its by far the cheapest way to go. A leak down test would probably catch that something was failing. The heads on mine were shot also.

Good Luck
Roger

Re: Dock Holiday
 

I'll bet that after we look at our heads after 100 hrs w/ the Cometics gaskets - all will all look fine. Glad to hear everyone else is having good luck with them also.

Joe

check them good,remember,the EFI motors shouldnt detonate with the computer controlling the timing,maybe youve got a knock sensor that failed and possibly didnt tell the computer to retard,every one I've come across was due to overheating and the gaskets may not have failed instantly,but did within a few hrs depending on how hard they'ed been run,had a 425 due the samething,caught it before it ruined the block and piston,but ruined the head,turned out the plastic pump housing had broken one of the vains on the intake side of it and never got hot,just had a little less volume and caused the gasket to fail.....

Quiet Storm
 

My gasket look exactly the same as yours did. I am taking pictures later today, and will be posting them this evening. Sounds like the same issue. Did you ever find the source of the problem or are all signs pointing towards gasket failure?

Jeff

Jeff

We found no reason why they failed yet. The previous owner of my boat lost a electric fuel pump just before he sold it. I thought it might be related but the port side engine was real close to failure also. The thin part of the gasket was pushed to the side. The leak down test on that engine was showing valve problems. So its getting a valve job and new gaskets also.

Roger

I agree with Formulafastech, to replace the gaskets without finding the cause of the original failure will most likely result in another failure.

If anyone is still looking for a pair of complete 500 EFI heads, blast me an email and I may be able to help you out.

[email protected]
www.adivanman.com

So far we can not figure out what happened. The only conclusion was gasket failure. Looking at the gaskets from both heads shows that the gaskets wore out between the cylinders, I have no idea why. Im not a motor guy in anyway and can only rely on what im seeing and hearing from the mechanic, and others that were willing to look. The merc rep was out yesterday, it will be intresting to see his take on this. It looks to me like the gaskets just wore out over time due to heating and cooling maybe. But what do I know? I took a bunch of pictures today and will post them later. Maybe one of you can help me fill in the blanks. That would be cool!!!!!

Here's the pics
 

Well here are the pics that I took today. Maybe this can shed some light on the subject.