Head Gasket In HP500EFI Casues Failure?
 

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.

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.

Another

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How Long Till She's In The Water Again
 

1

Man major melt down. Are you running water pressure gauges or has it been checked? With that rig I bet you run it with the throttles pinned WOT quite a bit. :D If I had that I would be anxious to get back on the water to. Really I am that way no mater what! :rolleyes:

The severe damage between 5 and 7 looks like pre-ignition damage. The engine firing order puts extra heat between those two cylinders. Was the base timing set to spec or slightly advanced? The knock sensor only compensates and retards a limited amount. Are you using stock ecm's or modified? What is your water pressure and do you have sea strainers with reserve water capacity (helps prevent hot spots and steam pockets caused by aerated water).

That looks all too familiar. I'm going to replace the knock sensors just to be on the safe side but the question of just what caused it is a nagging one. I was also planning to put in pressure switches that would alert me it the fuel pressure dropped below a certain pressure.

I guess I have to consider myself lucky. The damage to my engine was much less than yours. I can't wait to hear what Mercury tells you.

I was bouncing around on E-Bay and came across these heads. Maybe they will help you if Merc doesn't cover you.

http://cgi.ebay.com/ebaymotors/ws/eB...category=31286

I overheated a BB Chevy engine badly many years ago at Watkins Glen and burned a pathway between two adjacent cylinders. My guess is overheating and/or preignition. Just a blown head gasket usually does't melt pistons.

that motor got hot,the pistons and walls were washed clean w/unburned fuel,the head gaskets have been leaking for a while,that didnt just happen in a few minutes,you need to open your cooler up and tear your pump down and inspect it,youll probally find the cause there!

I have a couple of sets of iron rect. port Merlins for sale in the bulletin board classifieds. Upgrade when you repair.

I was freaking out over this and called a good friend that is a certified Merc mechanic that has treated me right and I really trust.

He told me to calm down, that he is NOT seeing anything like this out of 500's. In fact he menetioned several with EFI motors with 300+ hours he knows of running strong.

He said the only time he sees this type of problem is when the engines have been overheated!

Any thing can happen to any engine at any time, but I am going to get running mine. They are under warranty and hope for the best.

Troutly,

I am not doubting you, but I would think that if that were the problem, you would see the same issue with Mercs' other motors. Why just the 500???

Water pressure at idle is around 3-5 psi and while running is between 14-20 i think. But there was diffently water presurre and water flowing out the side of the boat from where it leaves the dry exhaust. I do have one strainer for each motor. The motor never got above 190 degrees and was then shut down. We have also checked the impellor in the water pump housing and it looks good also. Although it was replaced at one time as the wear on the housing and impellor are not the same. Not sure why someone would just install an impellor only and not the hole housing, but the proof is there. There is not signs of overheating on the block or head, but that is the only conclusion that we can come up. Is there a way to have the knock sensor bench tested. The truth will come when we pull the heads of the opposite motor and see those gaskets. If they look similar, then something is really screwed up.

3DO

Same exact thing happened.
 

98 500 carb motor 220hrs, dont have firing order, but it
was the back 2 on port side. 5/7?
Burned a hole in block and head just like yours.
Had the boat traded in on my fountain just
waiting for it to come in, Gave the boat and motor
in pieces with a pile of cash to keep the deal.
Sucked, I believe it was mercs. problem but
good luck with that. Hope it goes better for you.
John

It doesn't take long for cylinder temps to spike and not be noticed on gauge. Steam pockets form and severe localized overheating occurs. Inadequate water volume and pressure along with over-propping and/or overloading boat will cause high cylinder temps. Cool water will pass through block and around steam pockets and show normal engine temps. The 500 EFI has been pretty forgiving overall because of it's low compression and moderate horsepower. It may be time to review overall setup and build a little margin into the system.