Engine cooling - Fresh to Salt water - SailNet Community
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post #1 of 18 Old 09-13-2018 Thread Starter
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Engine cooling - Fresh to Salt water

Hi All,

Was looking at a boat thats been in fresh water its whole life. I'd be bringing it to a salt water environment. I know next to nothing about diesel engines and received the below message from the broker. The boat is an Ontario 32 with a 2GM Yanmar. I've looked at another Ontario 32 thats in salt water that also had the original 2GM Yanmar. So I'm a bit confused as to why the one is fresh water would be different. Message below.

"Unfortunately the owner of has pointed out that his engine is directly cooled by sea water. In other words it does not have the usual heat exchanger loop combined with a closed antifreeze loop which most maring diesel engines have. This will likely eliminate this vessel for your needs since direct cooling in salt water would damage the engine. The only way around this would be a fairly expensive conversion kit and it may be quite complicated as well."

Any help is appreciated.
Jay
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post #2 of 18 Old 09-13-2018
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Re: Engine cooling - Fresh to Salt water

There were many raw water cooled engines that worked for years in salt water. My friend just repowered his Sabre 28 that had a 1980 Volvo MD7 in 2014 (after 34 years of use!). The engine that he pulled still worked, but the cost of parts to keep it going was killing him.

While it is better to have a closed loop cooling system, a raw water cooled engine will work.


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post #3 of 18 Old 09-13-2018
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Re: Engine cooling - Fresh to Salt water

The fresh water boat probably has a 180? thermostat as diesels like it hot. Bringing this to salt will clog the engine as it now needs a 140 thermostat. No biggie Each system has it's pros/cons. I prefer the HX way, particularly when winterizing ,,something we don't
do on the tepid left coast. (zincs??)

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post #4 of 18 Old 09-13-2018
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Re: Engine cooling - Fresh to Salt water

Quite simply, you will be running one of the most corrosive natural liquids on the planet through your cast iron and steel engine, when you move from fresh water to salt.
As above, you can take your chances and hope for years of service or add a heat exchanger, seawater cooling system and feel fairly secure that you will have a reliable engine when you need it. Engine manufacturers wouldn't go to all the hassle and expense to put heat exchanger systems on saltwater boats if we all got 34 years (or even half that) without.
If it was me, I'd probably look for another boat. There is no guaranty that the boat has indeed always been in fresh water.

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post #5 of 18 Old 09-13-2018
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Re: Engine cooling - Fresh to Salt water

For the record if I had a choice I'd certainly choose a closed loop freshwater cooled engine over raw water cooled.

But I didn't have that choice. My boat has a Yanmar 2QM raw water cooled engine, original to the boat in 1977. The PO good proper care of the boat and engine and I carry on the tradition. I baby it and it is going strong after 3000 hrs (and 41 years). I don't expect that it will last forever. And I have no doubt that a similarly maintained fresh water engine would last longer.

I'd say don't write off a sailboat because it has a raw water cooled engine. Just as with the boat itself, consider the care and attention that the engine has gotten over the years.

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post #6 of 18 Old 09-13-2018 Thread Starter
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Re: Engine cooling - Fresh to Salt water

Thanks for the replies. I've learned a lot today! Seems like many of the older boats out here in Halifax have raw water engines that are still going strong after many years. A friends 1976 Endeavour 32 1 cylinder is still turning over everyday without issue. As well, the Ontario 32 I checked out here has 1800hrs on a 2GM with no running issues. Seems like regular maintenance and flushing go a long way to keeping the build up to a minimum.
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Re: Engine cooling - Fresh to Salt water

Changing to HX is not rocket science .Understanding first and figuring out where what goes.Will need a separate pump, a HX down low to avoid air locking if expansion tank is built in to manifold. Engine will be happier for the attention and you will become one
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post #8 of 18 Old 09-13-2018
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Re: Engine cooling - Fresh to Salt water

There is a reason salt water vessels sell for at least 20 percent less than fresh water vessels.
If you really flush with fresh after every use you'll be ok. Chances of that are slim.

Capta is correct. Salt water is one of the most corrosive substances on the planet. Make sure you have a budget for corroded parts replacement.

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post #9 of 18 Old 09-14-2018
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Re: Engine cooling - Fresh to Salt water

Doesn’t one need to pull the thermostat to effectively flush a raw waste cooled motor? Not to mention, it needs to be running, so the cylinders don’t flood?

I’ve never had a raw water marine engine, only FW and Exchanger. I would think an annual descaling would be in order on raw water cooled, as well as winter pickling with a high quality antifreeze that had corrosion inhibitors.

I wouldn’t absolutely rule it out, but it wouldn’t be my first choice.

A broker talking a prospect out of a sale!!? You may have found a good one there.


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post #10 of 18 Old 09-14-2018
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Re: Engine cooling - Fresh to Salt water

Quote:
Originally Posted by Minnewaska View Post
Doesn’t one need to pull the thermostat to effectively flush a raw waste cooled motor? Not to mention, it needs to be running, so the cylinders don’t flood?
Our seaward 25 has an open seawater cooled cooling system on its 1gm10. I installed a "t" in the seawater line with a ball valve on it. The ball valve goes into a longish water hose that has a garden hose fitting on the other end. I installed a hose spigot valve in the bottom of a 5 gallon bucket to attach hose to. When I want to flush the engine after a trip in salt water (or just to run it on the trailer when winterizing), I close the thru hull, open up the ball valve, and fill the bucket with fresh water, and run it off that. Easy peasy.
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