Heat Exchanger Mercruiser 3.7

[85 searay seville]

Fired up the boat today and the heat exchanger is leaking from the rear. It looks to me as it is the gasket, at least that's what I'm hoping. It was not leaking this bad until I tightened up the bolt about a half turn. LMK what you think. Also how do I go about replacing it. It looks like I would have to remove the hose clamps and move the exhaust out of the way. I would also go ahead and change the front gasket too.

 

[alldodge]

Fired up the boat today and the heat exchanger is leaking from the rear. It looks to me as it is the gasket, at least that's what I'm hoping. It was not leaking this bad until I tightened up the bolt about a half turn. LMK what you think. Also how do I go about replacing it. It looks like I would have to remove the hose clamps and move the exhaust out of the way. I would also go ahead and change the front gasket too.

Do I take it that your engine is an 1985?

 

[85 searay seville]

Yes the engine is an 85 also. I picked it up form a family member and it only has 52 hours on it. It has been in dry storage its entire life. I know there will be some maintenance issues I have to fix and this one just came about today.

 

[stonyloam]

Take the center bolt out, and the cap should come off. Here is what it looks like https://www.mercruiserparts.com/Sho...64.png&inbr=908&bnbr=120&bdesc=HEAT+EXCHANGER Make sure the end cap is flat. It may have been distorted if over tightened. If you can get a wrench on the bolt and your hand back there you should be able to get it off.

 

[85 searay seville]

So I should be able to get it off without removing the exhaust? That would be great. So does it look like the gasket is the problem?

 

[stonyloam]

It does, it could be that it was removed at some time in the past, and not did not seal when put back on, or water was left in it and it froze and the end plate was distorted. Yeah pull the front one too, that wil give you something the compair too. Check for debris under the front cover, to make sure the tubes are clear.

 

[85 searay seville]

Just pulled them both off. Without removing the exhaust. The back one looked like it was torn a little around the indentions of the end of the tube. I am going to order 2 of them to be safe. I was running the boat on earmuffs and the water turned on about 1/2 way. Could it have been too much water pressure causing the leak? Just something else I was thinking of.

 

[wrestling coach]

The water pressure through your muffs would not be great enough to cause a leak at that gasket. As stated above be sure the end caps are flat and not dished out from tightening the center bolt too tight. Also as stated above be sure this exchanger was not left with water in it and it froze. Your profile does not say where you are located. In an effort to see the back of that exchanger take a mirror and a good strong flashlite and bounce the light off the mirror onto the exchanger as you view it through the mirror. Just a little tip. Or hold a camera back there and take a few snaps.

Dennis

 

[85 searay seville]

I am in Ga. I looked through the holes and got good light shining through. So I think I'm good as far as blockages. I drained it this past winter by removing the drain plug on bottom, so I know it did not freeze this winter.

 

[85 searay seville]

OK. So the new gaskets fixed the leak. How long can I run the motor on the ear muffs? Also how much water should be coming out of the exhaust port on the prop? I would assume ever how much it takes in comes out. I have a little water coming out but it does not seem like as much as what is going in. I ran it for about 5 minutes on the ear muffs and the temp got to about 130 on the gauge. I did not want to run it any longer.

 

[Bondo]

OK. So the new gaskets fixed the leak. How long can I run the motor on the ear muffs? Also how much water should be coming out of the exhaust port on the prop? I would assume ever how much it takes in comes out. I have a little water coming out but it does not seem like as much as what is going in. I ran it for about 5 minutes on the ear muffs and the temp got to about 130 on the gauge. I did not want to run it any longer.

Ayuh,.... If ya got good water flow, turn it on Full, 'n run it as long as ya want,....

Yes, what goes in, comes out,.....

 

[stonyloam]

It has a 160 degree thermostat so it should stabilize at about that temperature. Make sure the reservoir is full of 50/50 antifreeze, and the hose to the expansion tank is hooked up. The expansion tank should be filled to the cold line, with the engine cold.

 

[85 searay seville]

Thanks Guys. It seems to be running good on the ear muffs. Now to get here in the water and hope for the best.