I concur...There is no indication that there was any detonation (no scarring on the pistons, ect). It definately did get hot based upon the discoloration of the cylinder walls and the gaskets. Heat would seem most likely in this case.

Thanks for the input
 

Thanks to everyone that has checked this out. Im not sure about the overheating. Could the gasket just have fryed due to the heat from combustion and finally gave out causing the flame to travel back and forth, or is this way out of line. Im not a motor guy so bare with me!!!!

TDO,

NO, the head gaskets are designed to take the heat of NORMAL combustion. They would not fail under normal conditions. Something very wrong happened here. As was said, simply replacing the head gaskets, regardless of what type you use, will most likely lead to disaster again. The real cause of the failure has to be found.

An interesting point to consider... when I had my heads redone due to poor leak down results the top end guy noticed something puzzling. The water transfer passages coming from the block on the center cylinders up to the heads was blocked by flashing from the original casting. He said that he had to drill them out(lightly). Ironically the center two cylinders on both of my motors had damaged the valve seats due to heat. He suspects that there was insufficient water flow due to this blockage. He also worked on another set of 502's and found the same thing. The guy was Eickerts top end builder and really knows his stuff..... I wonder if there is a defect on some of the blocks.

Sorry for the delay in getting back to you on this. I concur with everyone else about the overheat. The portions of head gasket burned across but not missing material indicate that the heads were warped at the time of failure. Since the are cast iron they may have flattened back out, but I would bet they are still warped. I suspect this engine overheated and the fresh water running around the temp sender gave you a false reading. Do you use crossovers or the stock thermostat housing/pump setup? You have to find out the root cause or the failure will reoccur.

It really sounds like you have 1 or 2 possible problems. I'm assuming fuel psi is in stock parameters and ocatne is at least 87.

First is water PSI. 15-17psi is low. Mercury Racing has a bulletin that calls for 25psi. I'm assuming you have a Spectre which runs high X dimensions. If you have the Mercury dual pickups on the drive, the side inlets release pressure. They can also suck air if there exposed to air. Plug them with 1/16" pipe plugs and you'll gain 5-8psi which is important.

Detonation is what caused the head gasket failure, if it burnt a piston, that was temp. The temp could have been from the detonation or from being lean which would've promoted detonation. I would assume that it was lean which then caused detonation which in turn creating tremendous heat and pressure. Pressure lifted the head, heat burnt the piston. From my experiance, the valves usually have a lot of damage if it's water related such as a steam pocket.

Thanks,
Dustin

I too have overheated at wot with a normal indication on the guage. I lost a exhaust valve seat in #3.

This is what happen to my sbc. The stock merc gasket blocks the steam holes between the block and the heads. the fel pro marine gasket has a hole to relieve the steam pressure.

Is the stock merc gasket that failed blocking any steam holes?

Are you saying a bad fuel pump could have caused this? If you look back toward the top of the link, I commented on having the same problem, but caught it (was lucky enough) before burning the bottom.

Just buttoned mine back up yesterday. New top end and all is fine. My gasket looked identical to 3DO's.

I feel your pain!!!!
 

Well, since these pictures looked so familiar I had to jump in.
I thought we could compare and maybe help diagnose. Mine’s a bit worse but I was running quite a bit of boost also.
I lost substantial water pressure during, or just before, a wide open run and 9 lbs of boost.
The results are what follow.
The pictures show #6 damage results. The Super Alloy exhaust valve was welded in the seat, which in turn broke the push rod, which then broke the intake push rod.
My head gasket shows a lot of bypass from 6 to 4, 4 to 2, 5 to 7 etc….
My gaskets, although they never blew the fire ring had blown the composite material on 2, 6 and 7 right into the lifter valley. This had probably been happening for some time because I would occasionally get a big blow by issue when under heavy boost.

Anyway, I’ve concluded that water (lack of) was my issue.
Number 5 piston was also damaged as was #2 with the rings butted and froze on both of those. More likely a result and not the cause although they were never gapped for a blown application.

Normal cruise water pressure is 13-15 lbs. When we limped back 12 miles on 5 or 6 cylinders at 3300 rpm cruise, I had 5-6 lbs. I never happened to peek at the pressure gauge before nailing the sticks but I’m sure that if I had, I wouldn’t have.
Dave

Chamber #6

Chamber

Well, It looks like everyone is concluding on the same fact. Overheating (Lack Of Water), or lean running condition. We are still waiting to find out what Merc is going to do before starting any work. Im going to have the ECU's, fuel injectors sent out and checked. After reassembly I will be sending both motors out for dyno so they can map out the ECU and make sure that fuel flow to each cylinder is correct. I no nothing about the ECU attached to the HP500EFI. We were at Carson Brummets shop on saturday, he had an EFI twin turbo charged motor on the dyno. There looked like there was alot of adjustment thru the entire rpm range with the ECU's running on the motor. Are the ECU's on the HP500EFI's the same were they can be reprogramed thru the entire range of rpm.

3DO

Nordic Heat
 

Sounds like were both in for a long winter!!!!! At least you block and heads are okay. Send me a PM and I will get you my office number and we can compare notes.

Jeff

I wonder if all these motors use the same electric fuel pump?

The fuel pump is mechanical in a HP500EFI. Thats one part that is actually still good on my motor. LOL.

Jeff

3DO, You laugh... but I've had two go bad over the last 3 yrs... It may not be good for much longer either! haha.

The feed pump is mechanical and the injection pump is electric. The mechanical pump drive (sea water pump drive) should be serviced each year when the impeller is changed. The drive cam uses gear lube that gets contaminated by fuel through slight leakage by pump. If not serviced properly the cam and pump arm will wear and not supply enough fuel to the injector pump.

Boatfixr,
What kind of gear lube is in the mech. fuel pump? The same lube as the outdrive?
MD

MD, use the mercury hp gearlube or better. I use Alisyn, Merc or Amsoil.

When the gear lube starts leaking it flows out the resivor hose attached to the pump right? Is that one way of knowing that you are due for a fuel pump. My port side (opposite motor) was starting to show signs of fluid running into that breather or overflow hose. Im not sure what the starboard motor (the bad side) fuel pump looks like. I do not that we will be replacing it upon repair. Do all the injectors generally get the same fuel pressure or if you start to lose pressure will certain cylinders be affected more then others?

3DO

Fuel in the hose is a sign of pump failure (bad). The hose is a safety device so raw fuel is not dumped into the bilge (very bad). When the supply pump is bad or when you are very low on fuel the injector pump pressure fluctuates and affects all cylinders.

Fuel Pumps
 

I saw both fuel pumps today and were told that they are both in good operating condition, but since they were pulled he reccomended replaceing them anyway. That starts to push me towards the overheating problem. The temperature never reached over 190 on the gauge, is the gauage that accuarte for cyclinder heat.

3DO

just a thought,but that can also happen from aireated water off the bottom of the boat,you may want to invest in some large strainers,which will help deaireate the water and also act as resevoirs for water,every time I rig a fast vessel I make the owners use these set ups,if your running excessive speeds with that thing and the water isnt clean entering the drive,or your X-demension is through the roof, or if you have seperate pick-ups with the angle on the bottom set wrong,youll run into that problem!I've run into this many,many times,ecspecially with new boats or boats that have just had faster power installed in them!
by the way,you mentioned only 14-20 psi on your gauge,thats way low for say 60-70 mph,that gauge should basically be pegged,for boats running over 80-90 you almost need a blow off valve on your resevoir tank,because of the increased water pressure entering your drive,to much pressure and it water will seep past the head gaskets!

Header Water Jacket Leaking?
 

3DO,

A friend of mine up in Canada had this exact same problem on his previous engine, a 550 hp 502 ci. He too had the head gasket fail between two cylinders (same cylinders as 3DO) and did damage to the block and head. While everyone seems to be blaming this on overheating, and / or to rich fuel mixture... no one has considered hydro lock or reversion. What happened to my buddy was that his exhaust header inner tube had cracked! Every time he shut the engine off, a little water would enter the cylinder, if the exhaust valve was open. Then on start up it hydro-locked and blew the gasket out between the other cylinder! Might be worth looking into.

Good luck.

-Bayley

OA, I think you hit the nail right on the head!!!!!!
When I installed my supercharger I also installed a crossover with a thermostat and bypass setup along with a transom pickup. I also installed a pressure relief valve that I thought I would surely need running high speeds with a thermostat.
Well my pressure was never solid and in hindsight I should have addressed the problem right then. I never so much as cracked the pressure relief valve and my initial cruise pressure was about 14 at cruise. This would fluctuate seemingly with the opening and closing of the 120 thermostat. When it opened it seemed that my pressure would drop below 10 and near 5 at times.
Like I had mentioned earlier, after the melt down we limped home and had only 5-7 lbs of pressure. I never checked before I nailed it so I am assuming it was not adequate!!
I think I’ve had a problem all along with my pickup situation. My boat has a step and no sea strainer and never generated enough pressure to require opening the pressure relief valve.
I have just ordered a sea strainer and will be addressing the pickup situation very closely.

Has anyone heard of or tried the thermostat setup from Rex Marine with a cold thermostat on a blower setup?

http://www.rexmar.com/page160.html
http://www.rexmar.com/page161.html

Thanks,
Dave

I'm a rex dealer also,that would work but if you read it it states ,combustion chamber temp to low,not a problem you should be encountering with a blower motor,that blower should have an increasingly high combustion chamber temp,thats why they recomend removing the stats for blower motors,helps prevent detonation!its basically a t-stat housing with a bypass,instead of your cross over having one to your stat housing!
you might rather address where your picking up water from!

OA,
with my setup I need to maintain 100-120 temps for my ECU to work as desired. We have very cold Spring water here in the Rockies (38-45')
That's why I thought maybe that housing with a 120' thermostat would work. It seems that when the thermostat is open it forces all of the water through the block by closing off the bypass.
Just a thought...
Dave

if your running a stat now,you should have a cross over w/ bypass hose,try restricting your bypass hose a little bit,that should help,it should keep your exh wet until your motor comes to temp,and force more water to the motor!
geese,thats some cold water,no swimin there!

you know another idea to maitain temp in that cold of water depending on what exh your running,on my little cimmaron I have a 356 ci w/a 671 TBS with a berkley pump,and I am running with no stat and it is plumbed like this,the water enters the manifolds which have solid gaskets on the risers(blocked off),the water is pre warmed and exits the manifolds to the front of the block and exits the t-sts housing,and dumps into the risers and exits,this thing maintains almost 140 degrees constantly.....it all depends on what type of exh your running to be able to preheat the water!its only 16' and man what a ride!

I have one M& M strainer per motor. It seems that I had good water flow looking at the dumps over the side of the boat, and the water pressure on the gauge. Im not sure what my water pressure is at WOT, I know I have seen it around 15-17 but at lower rpm's, I have always paid more attention to Oil Temp, Oil Pressure, & Water Temp, assuming that I had lower water pressure it would show on the water temp gauge. I have never had a overheating problem with the starboard motor. The port motor got real hot and alarmed once, after replacing the water pump impellor and housing it was taken care of that happened a about 5 weeks ago. My boat generally runs around 160. The day of the failure it got up to 190 and we turned the motor off, the only reason we even knew something was wrong was the smell of burning oil. That does not seem hot enough to cause this failure. Mercury's opinion is that it looks more like an overheating issue also. The motor has never been overheated in the time that I owned it. If the motor was overheated prior to my ownership, would it take time for the gasket to burn out? around three months or 40 hours of use.

3DO

no,it should have let go sooner,how big are your strainers,you may need to upgrade to larger capacity strainers,theyll deaireate and act as resevoirs when your in the air.....and you had better pay close attention to your water psi when shes reassmbled!

They are the large strainers from M&M. I will be definetly be paying closer attention in the future. I still do not think that I was running low on water pressure, but you never know. I have never had a cooling problem before. You would think that the water temp would get real hot and there would be a reading of high temp on the gauge, if the pressure was low. Im stumped, im just hoping I can somewhat pin point the problem to avoid future problems.

Thanks to everyone that have thrown their opinons out there, It has really helped with the on going problem, and what to avoid in the future.

3DO

The problem with thermostats is the block psi going all over the place. We don't run stats, customers want to alot of times, but we run a restrictor instead. With a stat, you may have 30psi while it's closed and when it opens psi can drop to 10 then back, etc. This is one reason for installing all the holes in them, so there always bypassing.

From countless hours of research, we relieve the back of the block which makes the motors much less acceptable to steam problems. With a cross over, the water is going in the front of the block and can instantly go up and out. Only PSI makes the water fill the back cavities and only more PSI makes it move forward and out. With the relief, it bleeds out. It still takes psi, but by no means as much.

3 days only,
Your wasting your time sending the ECU away and you don't need to tune it. They don't vary. Dynoing will only help if somebody has the ability to diagnose the problem, if you start tuning (only a few can with MEFI3) and don't find the problem, it will just happen again. The ECU's are set on the safe side and do not vary or change.

Thanks,
Dustin

Dustin,
could you clarify what exactly you mean by relieving out the back of the block?
Does this mean tapping holes in the back water passages on the intake manifold and dumping a hose to the exhaust. What size hose? 1/4?

Thanks,
Dave

Crossover Cooling?
 

Dustin,

This sounds like a much better way to cool the rear of the motor. Is there a kit that can be installed to complete this, or is it know how. Im not sure if my mechanic has any idea about this! What is the benefit of either running a stat or not? I was under the impression that the ECU adjusts the mixture or something under a certain temperture.

3DO

Can you either say more about this or e-mail me with your phone number and I'll give you a call. I might have had this problem. Thanks, Joe
[email protected]