454 Merc overheating, PLEASE HELP!!!
 

I hope you might be able to provide some advise. I have just bought a 1995 272 Islander Baja with a carbureted Generation V Merc 454, SR number OF413462, with a Bravo 1. The first 3 times I have had it on the water (fresh water only boat) it has overheated. The first time I took it out it overheated, 230 degrees F, right away. As soon as I heard the warning buzzer go off, I shut the engine down and then heard every cylinder fill up with water (this boat does NOT have through the haul exhaust). The engine was very hot (boiling water when splashed on the block, but there was NO water in the engine compartment and NO water in the engine oil). I towed it to the marina and they rebuilt the fresh water pump (the veins on the old pump were all intact and looked fairly good) and replaced the bellows boot. Took the boat out for the second time and the same time happened, but this time it would get hot only if you ran it at half to full throttle. If you went back to idle or lower throttle, the temp would go back down. I took it back to the same marina and asked them to replace the recurculation water pump. They did not and said that would not be the problem. They went through it again and found no problems. They checked every hose looking for restrictions and found none. They did replace the thermostat. The next time I took the boat out we ran it for 3 hours, at full and half throttle, and had no problems then all at once, it got hot again. I turned the engine off and heard the cylinders gurgling and belching and filling up with water again (again no water in the engine compartment and no water in the oil). I pulled it to my business( I own a trucking company and have our own diesel repair shop). We did a compression test and showed good compression on each cylinder, thus somewhat eliminating the possibility of a blown head gasket. Again with no answers, I took it to a different marina. They removed the circulating water pump and said it looked good. They also looked for restrictions in all the normal places and found nothing. They were stumped and did not know what to try next. I picked it up from that marina and took the boat to yet another marina and had them look at it. I had them replace the exhaust flappers with a new style (although the old ones appeared to be just fine). They also did a leak down test and said that it leaked compression in between three cylinders. I picked the boat up, brought it back to our shop, and removed the engine. I pulled the heads, the gaskets looked just fine, with no signs of being blown. I had the heads magnifluxed and they tested out just fine. I pulled the frost plugs and thougt that the block might be full of sand however found no sand inside. Needless to say, I am at a total loss as are the 3 different marinas that looked at the boat.

Would you have ay ideas as what to try next? I would love to fix this issue while the snow is on the ground so I can actually BOAT in the summer. My thoughts next are to replace the exhaust manifolds and risers. If they are cracked, I could see how water could be leaking out, across the intake manifold, and into the cylinders. I also am planning on replacing both the recurculating and fresh water pumps as well as any intake water hoses.

I would be open to replacing the heads or exhaust manifolds if it would resolve the problems. Money is an issue, but ultimately I just want to get the problem fixed. I plan on putting in a new cam and intake manifold while the engine is out.

Are there any intakes on the Bravo 1 drive that could be blocked or plugged? Each marina that has looked at the boat has told me that there are none that could be blocked.

Any ideas? Where would you look? If I am to replace the heads, intake manifold, cam, exhaust manifold, water pumps, ect… What would you suggest?

I sincerely appreciate your help.

Thanks,

Adrian, The bummed Baja owner in Iowa!

Re: 454 Merc overheating, PLEASE HELP!!!
 

I had a similar problem on a 383 stroker motor, just blowing water out the exhaust (truck), while you have the motor out have you looked at the cylinders for cracks? and also check your intake manifold. I've seen sometime where overtorking puts stress on it and a crack underneath lets water leak into the heads then down past the valves. hopefully its not cracked cylinder walls, but check there as well. That would explain a leakdown as well.

Re: 454 Merc overheating, PLEASE HELP!!!
 

I had a problem similar to yours and found that my oil cooler was clogged causing a restriction. I pulled the end cap off and cleaned out the tubes with a welding rod and the problem was gone.....Might not be your problem but worth a look.

Re: 454 Merc overheating, PLEASE HELP!!!
 

well ....mine did the same thing ...ok at slow speed or idle ....got hot when you got up on a plane and it was the thermostat ... I see you changed that ..does it have the stock cast iron exhaust ? if so ...check inside and see if there are signs of water running down the risers back into Exhaust Manifolds ....I would Def change the exhaust ...

Re: 454 Merc overheating, PLEASE HELP!!!
 

did any of the marinas inspect the water inlet hose in the gimbal?there ia a insert
on this hose that either fails or gets clogged

Re: 454 Merc overheating, PLEASE HELP!!!
 

They claim they inspected the inlet hose by the gimbal.

Re: 454 Merc overheating, PLEASE HELP!!!
 

i would look at the exhaust. Common for the original cast iron manifolds to fail and cause internal water leaks.

Re: 454 Merc overheating, PLEASE HELP!!!
 

Check the hose from the Gimbal to the water pump. Is it reinforced or has it been replaced with the wrong type of hose that may be collapsing when the pump is running higher rpm's?

Re: 454 Merc overheating, PLEASE HELP!!!
 

Where the heck are you boating in Iowa in in the middle of winter??????

First suggestion would be to find a marine mechanic that you trust and that knows what he is doing. The ones you've been to are chasing a ghost

What do you mean when "rebuilt the sea pump"??? Did they just replace the impeller or did they install a complete kit with new housing???? If they didn't replace the housing and its worn, it won't suck in enough water at higher rpms.

I hope you're not hearing water in your cylinders, as you say. If there's H2O in the cylinders and has been several times, you'll need a rebuild. You might hear water boiling in the block????????

My guess is you've got/had a restriction somewhere that is moving around enough to let enough water in intermittently. You also could have had several other problems get created by the original overheat. You should have a 140* in that engine. Mine would never get above 160* on the guage.

Re: 454 Merc overheating, PLEASE HELP!!!
 

God no I am not boating in Iowa now, my problems were from late summer and I am just now taking another look at the problems. The marina “rebuilt” the sea pump by replacing the guts and impeller. I do not believe that they replaced the housing. I had water in the cylinders. When I pulled the plugs, I blew water out of each cylinder. I have pulled the heads, and the cylinder walls do not look bad at all. A light hone and they should be fine. I believe we put in a 140* thermostat. We have looked everywhere for restrictions but still do not find any.

As far as finding a mechanic that I trust, I am not moving around out of disgust of the mechanic. The boat has been taken to different mechanics because they all seam to be at a loss as where the problems lie. Thanks for the suggestions.

Re: 454 Merc overheating, PLEASE HELP!!!
 

Back to the basics. This problem should be easy to find if you have that much water. This is no hairline crack somewhere if you are filling cylinders up. First question, Are they the same cylinders each time? Did you take the center risers off and look for sign of water leaking down? If you are getting water in the cylinders you are getting water in the oil :(

Re: 454 Merc overheating, PLEASE HELP!!!
 

When I said that I was not getting water in the oil was while the engine was running. After the engine overheated, got turned off, then you could hear the cylinders girgling and filling up with water, THEN yes you would have water in the oil after some time because it would leak down past the rings. But as far as driving the boat and checking the oil for water, there would be none. I have magnifluxed the heads and all look ok. I have sealed off one of the manifolds with a block off plate an pressured to 8 PSI and do not have any leak down. I am about ready to try the other exaust manifold now.

Re: 454 Merc overheating, PLEASE HELP!!!
 

***uming the heads are good (via your magnaflux test)
And the cylinder liners aren't cracked
And the headgaskets aren't leaking (you said they weren't)

Then you can only be getting water in the cylinders from the exhaust side or the intake side.

Cracked, or leaking exhaust manifolds should not cause overheating.
A leak in the intake water crossover can cause overheating.
The incorrect headgaskets (or the correct headgaskets put on "backwards") can cause overheating.
Incorrect coolant hose routing can cause overheating.
Weak springs in the popoff balls on the t stat housing can cause overheating.
An automotive thermostat (no air bleed hole) can cause overheating.


1) Pull the water hose from the t stat housing that comes from the oil cooler. With the outdrive in the water (not on muffs) fire it up and rev it to 2500 for a short spell. You should see an impressive flow of water. This will rule out any weirdness from the outdrive pickups, through the raw pump, and thru the cooler. Not safe to ***ume there's no problem there. Much better to witness the stream of water..

2) Since you are getting the cylinders full of water, there is either a crack in something OR you are overpressuring the block. Since all cylinders are filling up, my guess is a crack or bad gasket seal in the exhaust risers.

But that isn't causing the overheating UNLESS the exhausts are packed full of crap and are restricting the flow of water out of the motor,

best of luck

Re: 454 Merc overheating, PLEASE HELP!!!
 

Load that turkey up and let me fix it for you, i see a few opinions that are possibilities, however if you did a leak down you should have been able to draw a decent conclusion of where your leak down was going, it can only go so many places, too much disassembly not enough figure out was used in your search for a repair.

Re: 454 Merc overheating, PLEASE HELP!!!
 

I'm guessing the overheat is due to a collapsing water line (before the pump) if there are no obvious restrictions. As Scott pointed out, the wrong line will collapse but the correct ones deteriorate too. I've seen normal appearing external lines with delaminated collapsing innards. BTW, they usually idle fine but only collapse/overheat at high rpm.
As for the water, was it in all the cylinders? That's acually hard to do! Overheats can easily cause failed head gaskets. Leakdown would be my first test.
Gary

Re: 454 Merc overheating, PLEASE HELP!!!
 

Since both banks of cylinders are filling up with water I would have a hard time believing two head gaskets or two exhaust risers go bad at the same time. The overheating has to be related to water coming back into the cylinders. Gut feeling is, there has to be a restriction causing the water to NOT circulate causing it to overheat. :( The water must exit somewhere coming back into the exhaust. What are the chances something is causing it to backup in the Y pipe of the exhaust, forcing the water backup through the exhaust risers? Ok how about this you have one flapper in your Y pipe that is sticking. This could cause one exhaust manifold to fill with water. Water would then go thru the exhaust cross over in the intake manifold to the other set of cylinders. Far fetched?
I am land locked in Omaha :eek: . I also have a complete set of exhaust risers if you feel you need to replace them.
JIM

Re: 454 Merc overheating, PLEASE HELP!!!
 

Everyone, thanks for the suggestions and please, keep them coming.

To Jim, I also thought that the flappers could be the problem, wither they were sticking open and allowing water to be sucked back into the engine after it got how and thus filling the cylinders... OR the flappers might be stuck shut and not allowing the exhaust water out thus causing a restriction. Because of these two possible scenarios, I replaced the flappers with a new style (the old flappers looked just fine and opened and closed freely) and the problem still exists.

Good idea though!!!

Re: 454 Merc overheating, PLEASE HELP!!!
 

I'm pretty much with Gary. I would add the transfer tube in the outdrive should be looked at for twisting, collapse or clogs. See pic. I suspect the water is coming from the engines backspinning due to preignition when they are shut down in over heat mode. Eccentially your exhaust valves turning into intake valves for a 1/ to a 1/2 revolution. That is why you are able to clear the water and go again with no apparent issues, until whatever the root problem is recurrs. The only concerning thing to me if my scenario is true would be the quenching the exhaust valves are getting when they suck water back in. May make them brittle and untimately shatter at a most inopportune time.

BT :cool:

Re: 454 Merc overheating, PLEASE HELP!!!
 

Blue Thunder,

On the pic you provided, I would like to check that hose inlet that you are pointing at. Can I simply take the 6 bolts (I think that is all it looks like there are) that are holding the drive unit to the housing, and pull the drive (if this is what I am to call it) out? I mean, is there any special way to disassemble or reassemble this or is it something a qualified tech should do? Mechanical handiness is not the issue, I just do not want to remove something that will cause more problems down the road.

One question I have always asked the marinas is that is seams to me that the first place I would look for a problem would be an obstruction in the Bravo 1 drive, where the water intake is. The first marina replaced the bellows boot, but since then, I do not see or recall where the other repair facilities have looked at anything in this area other than maybe a visual check. Where is the water inlet on the bravo 1? What should I look to check for obstructions? By removing the drive unit, will I b able to see the problems/ obstructions that might be there or could they be hidden in other areas in the drive that one can not easily access?

Thanks again for all the advise!!!

Re: 454 Merc overheating, PLEASE HELP!!!
 

If you are handy I would definatly remove the drive and inspect this hose. While the drive is off you could also grease the ujoints, check the gimbal bearing and check engine alignment. As long as the engine alignment is ok, the only trick to removing.installing the drive is the shifter cable, shown on the right of my pic. I put my shifter in nuetral, remove the nuts and slide the drive back watching to make sure the clasp unhooks on that ball on the end of the shifter cable. Once it is clear the drive should come off easily. Of course you will have already removed the trim cylinder mounting bolts before doing the above. Reinstall in reverse order. Install new orings.

These are all things you need to learn how to do anyway. But if you don't want to do these now, remove the intake water hose from the transom inlet. Get a garden hose and shove it down the hose. Turn the water on. Start the engine and making sure water is flowing into the hose, see if you still have an overheating problem. It you do, the drive is eliminated as the problem. If the problem goes away, remeove the drive and start there. The water pickup point on the bravo drive is a series of holes at the leading endge of the housing on the left and right sides.

BT

Re: 454 Merc overheating, PLEASE HELP!!!
 

Don't forget to unhook the speedo tube before removing the drive. Easiest to do it 1st since you can raise the drive with the rams.

Also, what does replacing the bellows have to do with the water supply? I'm thinking nothing!

Re: 454 Merc overheating, PLEASE HELP!!!
 

Just to eliminate 1 area. Are you SURE the inlet hose feeding the sea water pump (the one on the bottom and to the side of the motor) is a hard wall hose? You will not be able to squeeze it by hand if it is the right hose.

Re: 454 Merc overheating, PLEASE HELP!!!
 

Doing the garden hose test will tell if this hose is the prob too as there will be virtually no suction pressure present. I forgot about the speedo tube, mine has never been there.

BT

Re: 454 Merc overheating, PLEASE HELP!!!
 

I would try to pressurize the cooling system, and see if it holds pressure. Block the outlets, and pressurize the intake. There is a nice gadget for use with automotive cooling systems, with a hand pump and pressure guage. You pressurize the system, and see that the guage doesn't go down due to a leak. You may be able to adapt it to your system with a bit of ingenuity. With water in the cylinders, it sounds like water is probably backing up from the exhaust side, especially since you notice this when you shut off the engine (no more exhaust blowing the water out).

Good luck!

Michael

Re: 454 Merc overheating, PLEASE HELP!!!
 

Dirthead, didn't you pull the drive when you pulled the engine????? I guess not.

I guess it could be done if you have enough room to move the engine forward. The drive will have to come off anyway to put the engine back in. You have to check alignment on the drive with an alignment tool. You actually adjust the angle/position of the engine in relation to the drive. This is crucial to the life of your coupler(where the drive goes into the engine). You might also consider replacing the coupler since the engine is out.

A lot of good replies so far, and the problem could be caused by a number of them or a combination of them.
If I were you I would replace the hose from the gimbal to the sea pump and rebuild the sea pump with a full kit that includes the new housing. These may not necessarily be the cause, but they could be contributing to the problem.

Re: 454 Merc overheating, PLEASE HELP!!!
 

BTW, where do you live/boat in Iowa????

Re: 454 Merc overheating, PLEASE HELP!!!
 

We are in SE Iowa, and typically boat at Lake Rathburn. Red Rock and Lake Coralville once in a while. We try to hit the Ozarks a few times a year.

How about you?

Re: 454 Merc overheating, PLEASE HELP!!!
 

Mo River and LOTO a few times a year. I only live about 8 miles from the river and my marina.

Re: 454 Merc overheating, PLEASE HELP!!!
 

Anymore suggestions??? I appreciate all the ideas, however most of them have already been looked into before I posted this initial question. I greatly appreciate all of your comments. If you have anymore, please fire away.

Re: 454 Merc overheating, PLEASE HELP!!!
 

Any more ideas?

Re: 454 Merc overheating, PLEASE HELP!!!
 

Have you checked ignition timing? Timing that is retarded will cause an engine to run hot, and this could also contribute to it dieseling when you shut it down while overheated - the engine will actually kick backwards for a rev or two, as BlueThunder mentioned. With prop exhaust this will most certainly suck water back up the exhaust into the cylinders. The little flappers might not be enough to stop this, either.

Just an idea...

Re: 454 Merc overheating, PLEASE HELP!!!
 

I don't mean to insult anybody with this , but are you installing the thermostat upside down? This causes overheating pretty quickly.

Just a thought.

Re: 454 Merc overheating, PLEASE HELP!!!
 

I think this was mentioned before, check the head gaskets, most are not left and right they are made the same, the water holes have to be cut in the gaskets on the rear of the heads, they have one cut in but not both. I had a problem similar and the heads were cooking, not knowing the gaskets had to be cut for the water.....

Re: 454 Merc overheating, PLEASE HELP!!!
 

One more thought, I run a water pressure gauge from the block, it will show if the water supply is getting cut off or restricted