Mercruiser 3.7 Heat Exchanger

Good Morning,

Could someone tell me a good way to clean, and "bench test" my heat exchanger. The manual tells me how to test while installed in the boat, but I want to bench test.
I read somewhere on this forum that acetone can be used for testing instead of pressure. I also read that an acid could be used to clean (not sure if thats a good idea), the manual says to use a brush in the tubes.

As always, I appreciate everyones help
Dave

Hi,
so this is the 4" heat exchanger on a 1986 Mercruiser 3.7 190. I just took off end caps and the inside of the tubes is nice and clean and clear. Looking down the raw water inlet and outlet, I can see some debris and scaling, etc. I have backflushed the unit and it doesnt seem to dislodge. What could I fill and soak it with to make sure the seawater side is clean. I can only imagine that any scaling or debris would be insulating the tubes and not giving 100% of the intended cooling.
I also would like to verify that none of the tubes are leaking.
Thanks

Re: Mercruiser 3.7 Heat Exchanger

I purchased a new to me 4" heat exchanger on the internet to replace my 3" exchanger. So I took it to a local radiator shop and had it cleaned and pressure tested. All was good. However in New York radiator shops can no longer chemically tank radiators and use some sort of ultrasonic method. I'm not saying that's bad. Perhaps where you are they can still chemically treat them. However if YOU want to clean your exchanger you could soak the exchanger in any of the automotive cooling system cleaners. Also white vinegar (slightly acidic) or CLR (more acidic) will work to dissolve and loosen scale. Flush and neutralize well when done. To pressure test you will need shop air and some plugs to check both the sea water side and antifreeze side of the exchanger. I wasn't there when they pressure tested mine so I don't know how they did that part of it.

Dennis

Re: Mercruiser 3.7 Heat Exchanger

Thanks,
I suppose CLR would work if I let it sit for a bit. I didn't want to cause any damage with a strong acid.
I performed the acetone test on my exhaust manifold and it was very simple and easy to do. I assume that the same test would work on the exchanger. If I fill the seawater side with acetone, it should run out the tubes that are bad (if there are any). Is that correct? I dont believe there is anything wrong with it, I am just doing some preventive maintenance.

Dave

Re: Mercruiser 3.7 Heat Exchanger

Live-liner said:

If I fill the seawater side with acetone, it should run out the tubes that are bad (if there are any). Is that correct?

Click to expand...

Not quite LOL, if you fill the antifreeze side the acetone will run out of the bad tubes. The seawater flows through the tubes, and the antifreeze flows around the tubes.

Re: Mercruiser 3.7 Heat Exchanger

LOL. Gottcha!

I HAVE A 1988 3.7 MERCRUISER WITH A ALPHA 1 OUTDRIVE, I AM LOSING ANTIFREEZE, NOT IN THE OIL OR THE BOAT? PLEASE HELP?

Jt, start your own thread, and we should be able to give you some help.