Mercrusier 3.7 coolant leak question

[Blackops]

Hello everybody, new to the forum and new to the boat world. I picked up a nice 1985 Stingray with the Mercruiser 3.7 engine. I have a coolant leak coming from the outdrive when the motor is not running. When the motor is running there is no leak. When I pour coolant into the riser tank is goes down rather quickly and I can see the green coolant leaking out of the outdrive where you would put the ears when running the boat out of the water.

I searched the forum for the past few days but could not find a post similar to this. I am assuming that I have a bad heat exchanger and it is allowing the coolant to leak out through the water cooled voltage regulator? When I pulled the seawater intake hose off of the rear side of the voltage regulator green coolant came pouring out fast. I would imagine that in a closed coolant system like mine the green coolant should not be coming from this area.

Thank you for your help with this and I look forward to your replies

-Blackops

 

[Bifflefan]

Re: Mercrusier 3.7 coolant leak question

the heat exchanger has a bad tube in it.
Pull it out and take it to a good radiator repair shop and then can find the bad one and plug it off. Then reinstall and have a great time.
These motors run about 140 at cruise and 150 running hard then cool right down when you slow. If your warmer than that check the impeller and the thermastat.

By the way, I have 3 tubes plugged in mine. Runs fine.

water cooled voltage regulator?

Nope, has nothing to do with the leak.

Welcome aboad.

 

[Blackops]

Re: Mercrusier 3.7 coolant leak question

Thank you for the quick response. Heading out to remove the exchanger now!

 

[Rocky_Road]

Re: Mercrusier 3.7 coolant leak question

Thank you for the quick response. Heading out to remove the exchanger now!

One more suggestion...the early engines had a 3" exchanger, that was traced to overheating issues. This was resolved with the introduction of the 4" exchanger.

Check yours for size...if it is the 3", then it would be to your benefit to upgrade to the 4". There are aftermarket 4" exchangers (new) still being offered!

Happy boating!