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EvinrudeJohnson 15 overheating problem

chetvaldes

New member
" It suddenly showed steam and

" It suddenly showed steam and I noticed the tell-tail wasn't squirting. I've tried running it with the thermostat cover off and the thermostat out- no water comes out. It did come out of the tell-tail however, for a while! Then it stopped. I looked at the impeller- it looked good. The water tube seems clear. One thing that bothers me is the exhaust that comes from the thermostat hole and the tell-tail(when it isn't aquirting)- is this normal? I know that the water outlet is in the exhaust so I can understand why exhaust my go back up the water system, but shouldn't the water pressure overcome that? Is this a water pump problem or could it be a combustion leak? If it is a combustion leak, is it the head gasket or could it be the exhaust cover? Or should I just tear everything down and replace these gaskets and the pump? How can I figure this out?
Cht "
 
"Chet,

If you ran the engin


"Chet,

If you ran the engine with the thermostat cover off, and did not have water pouring out from there, you definitely have a problem.

It sounds like you already have the lower unit off. Connect a garden hose to the water tube and see if the water comes out through the thermostat opening. If it does, there is a problem with the pump or the water passage leading to the pump.

"
 
"Chet.... If you are absolutel

"Chet.... If you are absolutely sure that the water pump is good, and you are also as sure that what you are seeing is exhaust exiting from the thermostat area, there could only be one cause.

Either the head gasket or the sealing area surfaces between the cylinder head and the block have become faulty. This would allow the combustion, the power from the explosion in the cylinder to escape across to the water jacket area, forcing its way down against the water pressure that's attempting to travel upwards. This results in a stalemate obviously and the engine overheats.

You may have some other problem but the above is the most common. I'd suggest that you remove the cylinder head and inspect that area.

If you had a problem with the exhaust cover (the inner baffle plate) or its related gaskets, the engine wouldn't overheat. The water would simply flow past those faulty areas and into the cylinders, pistons, etc.

Joe
"
 
" A common problem with the 9.

" A common problem with the 9.9 and 15hp OMC's is when there is an overheat, the rubber grommet sealing the water tube to the powerhead melts and closes off the water passage. You have to remove the powerhead and the exhaust tuner to replace it.
If, after removing the gearcase and trying to force water up the pipe, nothing flows, then pull the powerhead and inspect the grommet. "
 
" Does this mean I should pull

" Does this mean I should pull the powerhead anytime I overheat the motor? Can the tube grommet leak water instead of blocking off so that the water pressure doesn't make it to the power head? Also, After I inspected the water pump and reassembled it, I found that I could not make it pump by spinning the shaft by hand unless the pump was nearly submerged in water- it could not draw the water up the intake cavity at hand speed. Is this normal? One other observation- I noticed that the seal at the top of the pump was popped out of place. I reinstalled it with some sealant, but now I'm thinking it was pushed out by excessive pressure caused by the pump fighting the combustion leak from the cylinder head gasket leaking. Does this sound right? I'm pulling the head now and will see what's going on.
thanks everyone for your input.
Chet "
 
" i agree with seahorse , here

" i agree with seahorse , here in the barneget bay , the rubber grommet is what i am replacing most . i work for a guy who rents out boats with the older evinrude 6 - 7.5 hps and since ive worked there i have done about 5 of them . "
 
"Chet,

The engine should be


"Chet,

The engine should be deep enough in the water so that the water level is up to the pump. This insures that the pump will have some water inside when you start the engine. If the pump is dry when you start up, you can damage the impeller.

The grommet at the top of the water tube is a common problem that occurrs on this engine after an overheating episode. It starts to melt and covers the top of the tube. That is why I suggested that you try to force water up the tube with a garden hose.

You might find that the water jackets in the exhaust, on the port side of the engine are clogged also.

Whenever I replace this grommet, I don't use the grommet that OMC makes for this engine. It is too large and the top is too long. It extends above the top of the tube and invites the same problem if the engine overheats again.

I use a smaller grommet that fits snugly under the ridge that goes aroung the top of the tube, or I remove a little bit from the top of the grommet that OMC sells you, so that it does not extend above the ridge. Sometimes I simply cut off the part of the grommet that is blocking the tube and put the engine back together.

I have never regretted doing this and have never had to replace any grommet that I installed this way.

As for the drive shaft seal on the top of the pump housing, you did the right thing when you used sealer to hold it in place.

"
 
" Chet,

The exhaust plates


" Chet,

The exhaust plates are on the starboard side of the engine. I placed them on the port side in the last message.

Tony "
 
" I did pull the power head an

" I did pull the power head and did find that the grommet had closed up somewhat. And I did change the head gasket, altho it didn't look like it had been leaking. However, it's still doing the same thing. It's as though the water pump has trouble getting "primed", since once it gets pumping it seems OK. It just can't get primed when I have the thermostat cover on. And when the cover is off, I get that exhaust smoke puffing out. So I'm thinking that the pressure from this exhaust is keeping the water from reaching the pump- that is, the gases are going back down the feed tube and to the pump and pushing the water out. With the cover off, I relieve the pressure somewhat, and it allows the pump to prime. IF this is so, then where is the exhaust coming from? The only thing I haven't checked is the exhaust cover gaskets, so I might as well pull them apart and look at them. Anybody else ever had this problem? I might add that where I'm testing the motor the water level is just even with the bottom of the pump so the water has to be drawn up about half an inch. I will retry everything with a taller garbabe can to totally submerge the pump. "
 
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