What can cause head gasket failure on a HP500EFI. I recently had a major failure on my port motor. I was told it was caused by detonation. After further investigation and disassembly of the port motor we found that the head gasket was worn out completely between #'s 3, 5 & 7 cylinders. Between #'s 5 & 7 they are saying the flame traveling between the cylinders burned a round hole thru the block and head on center between the two. After the flame acted as a torch and burned the hole it then begin to heat and melt down the #7 piston prior to losing compression and then only running on 6 cylinders. I have been told by three differn't motor builders that it sounds like gasket failure and not detonation, and a machine shop owner that inspected the block and head stated that there is no sign of detonation in the motor, and that detonation was not a casue of failure. They have stated that the gasket wore out and casued the flame travel which resulted in this problem.

We pulled the head off the opposite side of the motor and the gasket on that sign is showing the exact same signs of wear as the other, and would have had the same conclusion if the problem could have progressed further.

The motors in question are 2002 HP500EFI's 168 hours. I have been told that this was a slow process which would have been undetictable unless the heads would have been removed and visually inspected. Is it true that there is no way to detect a failing head gasket until failure? What about Leak down tests, compression tests, spark plug readings, would any of that had worked?

All head bolts were checked prior to removal for torque and were fine. there is no sign of overheating either except in 5 and 7 obvisously. How could anyone prevent this problem? Better yet what will Mercury do? the motor are 4mo. out of warranty. There are coming to inspect the problem and hopefully will take care of this issue as it is in my opinon not somthing that could have been detected to avoid.

I had the exact same problem. 250 hrs. Buttoning the motor back up tomorrow. Makes me wonder if I should open up the other one and take a look.

Please give me a call, or e-mail me your number. I'd be interested in comparing notes.

Joe Pandak
[email protected]
713-222-7667 Office
832-277-3661 Mobile

Joe,

I was nice talking to you. I will give you a call when I have some more info. Good luck with the other motor better to catch it before it gets too late.

3DO (Jeff)

Jeff,

The gasket I was mentioning during our conversation, is made by Cometic (www.cometic.com) - 3 ply with teflon exterior. They're a bit expensive (around $75 each), but from everything I hear, well worth the money. They also have had great success using GM gaskets. They DO NOT use any Merc. gaskets etc...

You are welcome to speak with Joe at Owens Racing, here in Houston, TX. His number is: 281-485-5257. $500 for a brand new 500 EFI head, from GM (which I hear are difficult to even get these days).

I'll update you after looking at the heads in my other motor. It'll be a few weeks before I have it pulled apart.

Thanks for the call and good luck with Mercury!

By the way... Where did 3DO come from ?

We were in Miami last year for the boat show and valentines days. After three days of partying and clubbin all night I got sick, really sick fever and all. So they nicked named me Three Days Only becasue I missed out on sunday night at Nicki Beach, and could not hang. It just kind of stuck after that.

Jeff

I recently redid my HP500EFI's and used Cometics. I was told that they were the best and would hold up to the addition of Whipples.

Since talking to Joe earlier, I contacted two differn't motor builders about the Cometics gasket and was told the same thing. The Cometics gasket is diffently the right choice and should hold up alot better then the OEM gaskets supplied.

WOW, that really concerns me. I have 2002 model twin 500 EFI's with 170 hours.

Sounds like you have a lot of repairs ahead of you, including new head, and at least one piston?

What about your valve train, how do the valves and especially the springs look?

I do failure analysis for a living and would love to see pics of the damage. If you have any and can send them to me I might have some ideas for you. There is a slight possibility that detonation caused or contributed to the failure and it is imperative that the cause be found or you will roach the new motor.