Revert back to sea water cooling?

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rogerowen

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I've just purchased very nice 21' yacht with a Yanmar 1GM inboard engine that is fitted with a Martec Fresh Water cooling system. Unfortunately, the heat exchanger has failed and sea and fresh water are mixing within. Looking at the history for the boat - the heat exchanger has been replaced 4 times in 20 years, and these are not cheap items. As the heat exchanger would appear to be the weak link I am considering reverting back to the engine's original direct seawater cooling. Any advice gratefully received, thanks.
 
My engine's raw water cooled, though indirect cooling is also available. As far as I can tell, the only difference is that the raw water one has an anode in the side.

It's likely you'll need to change the thermostat. Fresh water cooled engines run at much higher temperatures than raw water, as sea water drops a deposit to clog things up if it gets much over, IIRC, about 60 deg.
 
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Shouldn't be a problem, you'll need to get a shorter alternator belt and a new thermostat - the thermostat for seawater cooling should be fully open at 52degC. As Stemar noted, you should have a zinc anode, but if your engine was converted from seawater you may already have one in place.
 
I'm also thinking of keeping part of the freshwater system and with an arrangement of valves be able to flush out the sea water after use. Might be a bit ambitious though.
 
rogerowen said:
Many thanks, why a shorter alternator belt?
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Doesn't your alternator belt drive the freshwater circulation pump?

Edit: I just looked up Martec and it seems you may have a 12v circulation pump, in which case no need to touch the alternator belt.
 
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IIRC, the 1GM is often raw water cooled and there's no great number of head problems reported. The one issue I'm aware of (think it's them :)) is a tendency for the water pump to leak and drip onto a steel oil pipe. Dripping seawater would do damage far quicker than fresh, and an oil pipe rusting through will definitely spoil your day. Not a big deal day to day, just something to keep an eye on
 
simonfraser said:
Local yard here does a great trade in fixing salt water cooled engines.
Mostly mobo’s which are imported / fresh water designed boats, engines corroded to bits.
Depends how much spare cash you have I guess....
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Ha, ha. Spare cash is definitely the issue here. A new heat exchanger is going to cost near on £1k (a little more than we paid for the boat). The fact that the boat's history indicates that it has already had 4 heat exchanger replacements does not fill me with confidence about the quality of the Martec system. If I do revert to the original seawater cooling, I intend to find a way of freshwater flushing after use.
 
KellysEye said:
We had fresh water cooling and the previous owner and I sailed over 20,000nms without the heat exchanger failing. I wonder if you need a higher qaulity heat exchnger.
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The Martec system is not particularly cheap - running to a higher quality one would unfortunately be unaffordable.
 
Graham376 said:
I fitted a Martec kit to a Berwick based MD11C and it worked fine for the 4 years I had it. Surprised your stack has given so many problems, is it plumbed correctly and did the fresh side have antifreeze/inhibitor added?
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From the history logs I would say that the previous owner was quite fastidious - but can't say if any chemicals were added to the system, although the are regular notes about anodes being replaced to the heat exchanger on a regular basis.
 
rogerowen said:
Ha, ha. Spare cash is definitely the issue here. A new heat exchanger is going to cost near on £1k (a little more than we paid for the boat). The fact that the boat's history indicates that it has already had 4 heat exchanger replacements does not fill me with confidence about the quality of the Martec system. If I do revert to the original seawater cooling, I intend to find a way of freshwater flushing after use.
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How much? They're listed here at €516. https://www.martec.se/en/group-1592940/group-1636596/group-1638167/article-14245729.html

What goes wrong with them, is it not possible to have the stack replaced?
 
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