454 overheating Bravo 1
 

I hope you might be able to provide some advise. I have a 1995 272 Islander Baja with a carbureted Generation V Merc 454, with a Bravo 1. Rebuilt the engine 2 years ago (got hot and cooked it). While rebuilding it, we put Aluminum heads, Lighting headers, roller cam, bigger carb, good pistons, rods, ect. The bock was magniflexed, and everything was fine. Basically built some more power, but with the real intentions of improving the reliability.

I have had the boat out twice this year. Each time when I am at WOT for about 2-3 miles, 62 MPH, 4900 RPM, the water temp climbs to 210. Water pressure is at 22-25, Oil temp at 140, Oil Pressure is 60 PSI. The water temp may limb more, but when I see it at 200, I idle down and watch the temp drop back to 160. In an attempt to fix the problem, I replaced the seawater pump housing and impeller (there is no circulation pump and this is in fresh water only) and did not find any missing rubber pieces. I also replaced the 140 marine thermostat for a 120 marine thermostat. These changes did not fix the problem.

2 year ago, I replaced the water inlet hose that goes over the top of the lower unit and back into the boat (this had a kink in it and is what caused the first engine to cook) so this hose is fairly new. The oil cooler is not plugged and at idle I have plenty of water dumping out my water bypass. When the engine gets to 210, the Lightening headers are still cool to touch. The oil has no water in it. The lake water temp in Iowa has only been 72 degrees.

Where would anyone start to look? I have thought about removing the thermostat and plugging the crossover hose (the hose that goes from the old circulation pump to the thermostat housing) but have not done that yet. I am just afraid of cooking another engine! Please any advice would be appreciated!

I think on that year motor there are two oil coolers...MAKE SURE THEY ARE OPEN....you will have to remove them and dig any debris out of them..it will not just fall out and prob not even backflush out, this is my first guess for your problem...however, you could be sucking air through your transom hose if it is not properly sealed...this type of symptom you are describing is typically a water flow issue..works fine at low rpms but when engine is running hard you have a high heat problem....btw..I would not run it for 2-3 minutes anymore @ WOT until you have found and fixed this problem...basically you need to track from your seawater pump all the way around and clean anything the water goes through all the way to your front crossover, you say you changed your t-stat so that area is already checked I guess...good luck

This boat only has and I am pretty sure that it only came with 1 oil cooler. I can not find any retrictions in it.

you and I need to talk and compare, I a'm running a 622 naturally asperated with CMI big tubes and a crossover, I a'm having very simular problems, 10psi at idle and 35 at 4000. with a standard 160 thermo it will over heat, Does your crossover dump into the top of the thermo housing?
as of right now I have drilled 4 1/8" holes in the thermostat so the water could pass, it's keeping the engine cool but is not the awnser to the problem, I think the water coming into the top of the thermo housing is cool enough to not let the stat open properly. feel free to call me. 435-820-0377
larry

Larry,

I will try to give you a call later today. Yes, my crossover dumps into the top of the thermostat housing. I have never thoguth of that, but at the thermostat housing having the crossover inlet, two outlets to the lightening headers, maybe the thermostat is not opening up.

Whaqt are your thoughts on plugging the crosover hose that feeds the thermostat housing and removing the thermostat?

Check the inlet hose adapter that attaches the inlet hose to the inside gimbal ring for debris or restriction. Comes off with two bolts. This has been know to cause similar problems in the past on that motor.

I can get the adapter off of the boat, but see no way to be able to look into the fitting that comes through the gimble adapter while the engine is in the boat. Any suggetions here?

Perhaps I am confused here but my crossover has eliminated the circulation water pump like I assume yours has and therefore my cold water inlet is plumbed into the block at this point. I have no cold water into the thermostat housing as you describe. The cold water is forced into the block through the crossover, then travels through the heads, through the intake to the base of the thermostat, where Procharger calls for the drilling of three 1/4" holes to allow for minimal water passage while the thermostat is closed. My cold water inlet does not pass through the thermostat housing. It direct connects to the crossover, as without the circulation pump, pressure is needed at this point to force cold water through the block. In the stock system you always had water going through the block as a result of the circulation pump (no longer there). What might be happening to you is that if you are passing the cold inlet through the top of the thermostat housing while the thermostat is closed the water is in fact forced through the crossover into the block but has no outlet until the thermostat opens or has a couple of holes. once the thermostat heats up there is no pressure differential to effect flow and no circulation through the block therefore no significant cooling. Solution!! plumb the inlet through the crossover and drill (3) 1/4" holes in the thermostat these handle overflow to the headers/dump during warm up. I will bet this will work as it does on my 500+HP application. If you are not as confident, direct connect to the crossover, take the thermostat out prior to drilling the holes and she should run so cool the gauge may never lift off the peg. Oh yes and do plug the current inlet on the top of the thermostat housing. My Mercruiser service manual has a flow diagram to support this idea. The small hose connection previously returning to the circulation pump from the top of the engine should have been eliminated with the initial crossover installation. You can call if the above has totally confused you Bob @ 530 587 4700

if you called yesterday, sorry I missed your call, I will be in town all day today, so try again. 435-820-0377 or 435-637-3304, from the way it sounds we are having the same problem. I tried removing the thermo, your engine will build up no temp and thats not good.

If you are refering to my suggestion of temporarly removing the thermostat, the next step is to drill the holes and put it back in. Does what I suggested make sense for Hoozeyurdaddy?

Barronbob,

What you are saying makes since. I am not really sure why my rossover has an outlet to feed into the thermostat housing... unless it is to insur that the headers are always reciving a constant supply of water. In any case this may be the problem. Let me ask you this. If I remove the crossover hose to the thermostat housing (by plugging both ports) and force all of the water through the engine and out the thermostat, will having (3) 1/4 inch holes in the thermostat be enough water to cool my headers?

Currently the water flows into my headers this way... From the thermostat housing into the header, out of the header into a T that has a valve on it to dump excess water out of the boat ( these valves are 7/8 ths compleatly open, essencially dumping most of the water out of the boat and allowing only about 1/8 th of the water back into the exaust to cool the rubber couplers. It is set up this way to keep excess water in the exaust and to prevent reversion).

My question or concern is this. When the thermostat is open, I should be getting plenty of water out of the T's and an adquate amount into the couplers. However, when the thermostat is closed and I only have the water coming out of the (3) 1/4" holes, will there be enough to adquatly cool the couplers with the valves onthe T's dumping most of the water out the bypass? I mean I risk the issue of reversion on on hand, and burning up the rubber couplers on the other.

Thanks for the help!

I can't answer your question as I am not familiar with the set up you describe. But I can tell you this. My rubber couplers have done fine however they do see all of the (3) 1/4" holes have to offer. What I can suggest is that you temporarily remove the thermostat, plug all hoses between the block and the crossover, have the only cold water inlet through the crossover, run the boat to see if your over-heating problem has gone away. Then address the cold thermostat flow to your headers with respect to your reversion potential. I am not sure of your exact configuration but if you have a direct connecting hose from the crossover to the top of the thermostat, it may be flowing too much. Place a valve in this hose, run the boat and begin to curtail the flow until the block begins to cool. If you see cooling beginning to take place because you are pinching off this return path and this might prove my theory. You also would not have to drill holes as this hose/valve combo will act as a variable by-pass allowing you to adjust flow pressure during hard runs and provide by-pass during cold start. I hope this is not getting too complicated.

Thanks for the help!

I will try this this weekend. One thing I have never understood is the need for a thermost in a boat at all. I have always been told that an engine needs some heat to run at opptimal temperature however have never been given a reasonable explination at to why. I am not arguing the fact that some temp is benifitual tot he engine to reach peek erformance. HOWEVER, how much is one reallly sacraficing on a 475- 500 HP engine by removing the thermostat cmpleatly and keeping the engine very cool? Is the sacrafice of a cool or even cold engine simply a small performance drop or is it a BIG drop..... or is the negative of running no thermostat simply more than a loss of performance (engine failure of some sort)?

I am just tired and quite simply worn out of 3 years of never ending fustrations with this boat. If I loose some performance but have the piece of mind that I am not going to cook the engine, so be it. I just want to go to the lake, have fun, and not worry. After I cooked the engine the first time, I rebuilt it with reliabilitly #1 and added performance a distant 2nd.

I understand the frustration. You don't want to hear what supercharging has done to frustrate my happy boating life. Here is why you do need a thermostat. Your engine fit tolerances are centered on an operating temperature, piston fit, ring fit etc. If you run cooler than spec parts will either be too tight or too loose causing wear. Please do not loose confidence as I do believe we are on to something here GOOD LUCK and keep the faith. If you need a boost or just want to have a conversation about what you are about to do please call. By the way I am not in the marine business. I am an engineer who deals with heat every day. Good Luck and Happy Father's Day if you are one.

Thanks alot. That means a bunch. I am a proud pa pa of a 5 and 2 year old, Hopefully Sunday will be an enjoyable Fathers Day at the lake for mom, dad, and the kids! Happy Fathers day to you also.

dirthead and baronbob
as of right now, my thermo housing has 3 ports, 2-3/4" outlets for exaust water and 1 #8 fitting in the top, at this point i'm not sure what the fitting in the top is for, the housing didn't come with a diagram,If I cap off the #8 fitting and run a non drilled thermo it destroys my water press gauge (40+psi) but when the thermo opens all is good until it closes again. If I drill 2 1/4" holes in the thermo, press is still a little high but workable, but the engine will not come to temp.
Now if I hook up what I think is a water supply for the exaust,
the #8 fitting on top of the housing, with a 1/2" hose from the waterpump crossover, water pressure becomes normal 15-20psi, the thermo will not open and the engine will overheat, with or without a drilled thermo, I'm not sure if it's because it equals the press. in the block or if the cold water is closing the thermo, I would think if it was equalizing press. I would see it on the gauge.
I am wide open to suggestions on this issue. I think baronbob may be onto something by restrcting the flow to thermo housing. merc offers a press. releif valve I'm going to look into.
you also need engine temp to evaporate condensation that an interal combustion engine creates.
Its been great chatting with you 2, hope you both a great fathers day.

hoozeyurdaddy,

The #8 fitting you are refering to in my oppinion is to have a hose from your crossover to the thermostat housing. This is with the assumption that you are using the (2) 3/4" outlets on the thermostat housing to feed your headers. IF you do not have this hose connected, Everyone I have talked to says it is a HUGE no no to ever run a thermostat even with a few small weap holes in it. The weap holes simply do not allow enough water through them to cool your exaust and/ or couplers. From what I have been told, if you are not running a hose from you crossover to your thermostat, you should remove the thermostat. This weekend I am going to try to remove the thermostat and plugth crossover to thermostat hose and see what happens. I called CP and spoke with them on this. They do not think that the crossover to thermostat housing hose allows anough water through it to cause the problems (not allowing enough water through the engine by providing an easier path of flow or by messin up the thermostat because of the cold water hitting the top of the thermostat) that we are guessing to be. Their position is that the fitting on the crossover that suppies this hose is 1) smaller in diameter, 1/2" and 2) on the top of the crossover tube thus it is not like the inlet water hose has a direct flow path into this hose. The water coming out of the supply hose comes into the crossover tube, then has to bake a tight 90 degre turn to go up the crossover to thermostat housing hose. They claim it allows enough water through it to cool the headers, but not enough to cause these issues. Having sold thousands of them, they feel if this was a problem, they would be hearing more talk about it. I understand their point, hosever I am going to try removing the stat and the hose and see what happens.

If this fixes the high temp issues, then I have though about making a set of plates with various holes in them to put where in place of the thermostat. THis would force the water through the engine, would allow constant water to pass to the headers, and may restrict the water flow a bit so that some heat is generated and kept in the engine. The size of hole in the plate would be determined by the tempeture that the engine reached and the PSI that the gage shows at WOT (keeping the PSI at 22 PSI).

What do you think?

You guys are really thinking now. The hole in the top of my thermostat housing has a temp sender in it. I would be careful with a plate for the thermostat might present other problems related to pressure over engine speed range. When I first installed my procharger I managed to blow the stock intake manifold gaskets and got milky oil as a result. Lots of milky oil threads on this forum. If you can make the thermostat work you are better off. Here is yet another idea. I have a heat exchanger on board for my domestic hot water. I rout hot water around the thermostat by taping into block water just below the thermostat in a factory port, out to the heat exchanger and then back to the top of the thermostat housing and thus to the headers. If you have ports near the bottom of the thermostat then plumb in a by-pass hose and put a ball valve in the flow. With this design you don't see the cold water coming from the crossover, you get to keep the thermostat action, no holes in same and you can adjust the amount of by-pass. BRILLIANT (I hope).

I can't believe I am sitting here, 5:30 AM typing this post. I awoke earlier this AM thinking about your situation and mine. My stupid heat exchanger hook-up is what has kept me from experiencing some of the problems you two are experiencing. After I blew intake gaskets in connection with my Procharger install I hooked up my heat exchanger, not knowing that it in fact would solve my temp. Control problem as well. Here is the theory. Make the only cold water inlet to your crossover with no way around it. I.e. Block the hose outlet now connecting to the top of your thermostat. This means that all cold water will have to travel through the block. Do not drill any holes in your thermostat and do have it installed. Find an outlet near the bottom of your thermostat and plumb in the same size hose fitting that you once had coming from the crossover. Once in place connect the other end to the top of your thermostat. Cool water is now forced through your block under all thermostatic conditions (open or shut). The flow that you previously had will still be there only now it will come from within the block allowing the thermostat to function properly. As the motor warms up the thermostat will open and lessen the effect of your by-pass but still be flowing into the dump scheme. I have a ball valve on my by-pass because I wanted to pinch off the effect of the bypass to keep my engine warm in start up, idle as well as under way. I suggest the inclusion of the ball valve but you may want to be convinced of proper cooling first. In summary: take the hose from the top of your thermostat and disconnect it from the crossover. Plug the crossover hole. Take this hose still connected to the thermostat and find a suitable fitting near but under the thermostat. Hook it up and enjoy a cool running boat. If the block does not come up to temperature install a ball valve in the newly created by-pass and turn it down slowly until you see the temp coming up. This system will work "I GAURENTEE IT" AS THEY SAY ON THE MEN'S WHEREHOUSE COMMERCIALS. I hope either or both of you are able to try this, AGAIN HAPPY FATHER'S DAY Bob

Dear Dirthead and baronbob
Yesterday my boat burnt to the ground, yes it was an accident, My right hand could not let go of the bic lighter I was holding on the fuel line. Thankfully it was insured.
Boy wouldn't that just brake your heart, (maybe-maybe not)
I'm sure there is a way to make this system work, ( I wish 1 of you would hurry and figure it out). the ball valve idea bob has is a good one, I respect what cp says, but why dont it work, If I connect the bypass hose to the thermo housing with a standard thermostat it overheats.
now that is how they designed it, why can't they tell us why it don't work? What are others doing different than me. I'm going to call teague racing and see what paul has to say, I will let you know
larry

Dirthead
How did it go?
Bob

Ok guys, here is the update... and the fix!!!!

I removed the stat and the hose that went from the crossover to the stat housing. Ran her hard and, as usual, water temp went to 210, oil temp to 140 after about 3 minutes at 4900 RPM. This left me in the middle of the lake getting the crap kicked out of my by the waves, scratching my head and not trying to cuss infront of the kids.

What in the hell could be going on here. I checked EVERYTHING I could think of..... I even replaced the water temp sending unit. The only thing I did not replace yet was the water temp gage. Then the light bulb went on.... AND IT PROABLY IS GOING ON IN YOUR LITTLE HEADS ALSO RIGHT NOW! Water 220, oil 140 which is just the oppisite as what they should be!

After a quick look I was right. Somehow the wire on the water temp sending unit and the oil temp sending unit got reversed! After a 12 seconds ( I had my 5 year old daughter count out loud as I switched them, just as a reminder or to rub it in, how such a HUGE headache this had become) the problem was fixed.

After it was all done, I was happy that it was resolved, but kind of ticked that it was such an easy fit.... which led me to be mad at myself for being ticked that is was such an easy fix!

I guess this is a simple reminder for ALL of us to not take the basic trouble shooting steps for granted.

Ok now it is your turn to weigh in and beat me down and to tell me how stupid I was! Thanks for everything!

Great news!! Don't kick yourself too bad as we all make simple mistakes. If you are still making yourself suffer then read my thread about putting my flywheel on backwards. Happy summer. My rig is really dialed now and we are headed for 9 days on Shasta.