Overheating 3.7 HELP

[DannyG]

I have a 1988 welcraft 190 with a 3.7. when using it at under 3500Rpm it is fine. If you run it above 3700 or pull a skier the water resivior will run dry. I have checked the heat exchanger by pressureizing the shell and tube sides independantly, there is no leak.all of the hoses are good. the engine does not miss or loose power when this happens. What do I need to look for. thanks

 

[Bt Doctur]

Re: Overheating 3.7 HELP

Explain again how to tested the heat exchanger.
The shell and endcaps are the raw water side. Unless you check the A/F side , you can still lose the A/F into the raw water side

 

[DannyG]

Re: Overheating 3.7 HELP

I removed the heat exchanger and end caps, Ipressurized the antifreeze side to 25psi no leak. then I installed the caps and filled the antifreeze side with water and pressureized the tube side to the same no bubbles and it held pressure.

 

[bhammer]

Re: Overheating 3.7 HELP

DannyG, do you have a 3" or 4" heat exchanger? The 3" are known to casue just cooling issues and why Merc upgraded to the 4". Doesn't explaine where your antifreeze if going though. Also, are you loosing water out the weep hole at the botttom of your timing cover? Where is the water / AF going if you know. Do you have powersteering with the cooler?

Up at the top of this forum is a post called "Adult's Only" head up there and download the manual for your engine. In there, is a great logic tree for troubleshooting cooling issues.

 

[DannyG]

Re: Overheating 3.7 HELP

I have put it all back together and found the weep hole pouring water. What now?

 

[cooter2506]

Re: Overheating 3.7 HELP

Sounds like another common problem of the 3.7. Cam shaft seal leaking. Pull the manual up from the Adults only section for you engine. That will help guide you thru this. Im no pro on the 3.7 but that is what I have seen on these forums as a culprit for leaking where yours is. Good luck and Welcome to Iboats.