Boatfixr

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.

Three Days Only

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

Offshore Addiction

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!

Bayley

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

Nordicflame

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

Offshore Addiction

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!

Nordicflame

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

Offshore Addiction

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!

Three Days Only

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

Offshore Addiction

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!