View Full Version : MD 7a Heat exchanger

03-11-2009, 12:12 PM
"I have a 1977 Volvo MD-7a engine in my sailboat. The boat has always been in fresh water, but now I want to take it to the coast. The engine does not have a heat exchanger. So, fresh lake water runs directly into the engine for cooling. Where can I find a heat exchanger? and... What do I need to do to make the conversion?"

03-12-2009, 09:33 PM
"I would say that if you have to ask, you should consult a pro. It can be done, but it is more than can be described on a web forum."

03-12-2009, 10:16 PM
"OK kevin, since you didn't appreciate my post (sent nasty e-mail), why not just ignore it and wait for somebody to post a Volvo manual?

You need a raw water pump to pump raw water through the heat exchanger and another pump (probably the one you already have) to pump the coolant through the engine. And the heat exchanger and hoses. And mounting bracket. And a way to dispose of the raw water.

Best bet; find one like yours with fresh water cooling and copy it."

03-12-2009, 10:46 PM
"I'm looking for valuable information, not useless rhetoric. Just as the intake has to be split, so does the exhaust. That is where you dispose of the raw water.
In the email I asked why you would post something that says nothing. You second post confirms that is all you know.
Please do not respond. You have nothing to add to this thread.
I am looking to gain some insight from an experienced person.
Thank you."

03-13-2009, 07:36 AM
"Your engine is 32 years old. Volvo very likely has stopped making parts for your engine. Call a Volvo dealer amd ask for the heat exchanger, tubing and bracket and see if it is available.
The engine is at the end of its life cycle. I would go ahead and use it in salt water until it dies which would likely be from some other condition before the salt became an issue. If you are really concerned, they sell flush kits that you can permanently install in your water line before the engine and you can flush with fresh water from a hose at the dock after you finish motoring for the day."

03-13-2009, 08:22 AM
Talk to Sendure Products in Fla. They make cooling kit for your application. Volvo never did. Kit has everything in it to convert.

03-13-2009, 11:49 AM
"Not to be confused with Kevin's post, Richard, but for my 1982 MD11C, Sendure's model is not a match. Do you have any idea who else might have made the one I have?"

03-13-2009, 01:39 PM
"Thanks Richard, I'll check with them.

Yes, Joe. The engine is old, but then so am I. It doesn't burn a single drop of oil between changes and the fuel burn rate is about 1 gallon every three hours; two hours when I go into a strong headwind. I will not let this keep me from running in salt water. I'd prefer to give the engine the best possible care whenever possible and expect the same in return. It has never let me down. The flush kit is a good idea that I had not cosidered and should work until I can adapt a heat exchanger. Thanks"

03-14-2009, 12:27 PM
"Joe, MD11 did have a kit from Volvo. Aftermarket could have been Lenco. Do not know if they are still in business. If you have a circulation pump that mounts above starter it is probably a Volvo system"

03-14-2009, 01:07 PM
Sen-Dure has two kits listed in their catalog for the MD-7A. I contacted them, but there seems to be a question whether they still make these kits. They said they'll get back to me early next week. The kits comes with an electric raw water pump, which is fine since the engine needs to be runny anyway.
Anyone interested the sit is:
http://sen-dure.com/ ("")"

03-14-2009, 01:20 PM
Thanks Richard. I do have the pump above the starter.

03-14-2009, 09:25 PM
"The once 'original' set for the smaller Volvo engines was made by a company called Martec. A combination of Sendure and a Johnson Pump electric circulation pump or the fresh water circuit. Here is the link for the Johnson pump.
http://www.johnson-pump.com/JPMarine/products/circulation/index.html ("")
Just build Your own system, keep the manifold raw water cooled, use the original pump for raw water and hook on an exchanger.
Do not use impeller pumps for fresh water circulation!"

03-17-2009, 05:58 PM
"Thank your Morten.
Sen-dure contacted me. Although Sen-Dure does not make the kits for an MD-7A anymore THEY DO still make the heat exchanger!

Consistent with Morten's comment, Sen-Dure recommended Johnson Pumps for this application too. They even emailed me a page from the catalog with the recommended pumps highlighted.

Thanks to all! This is definitely a doable project. The heat exchanger is on order. I'll order the pump once I have received that to ensure the proper hose connections."

03-18-2009, 08:52 AM
I agree with Morten but in your application there is no practial way to avoid using existing pump for coolant circulation. Look into getting what Johnson calls a piggy back pump to mount to your existing pump for raw water into system. Johnson # is 10-24143. To use you will have to get a longer shaft from Johnson for your existing pump.