Yanmar 3GM heat exchanger

[Andrew_B]

My boat has a Yanmar 3GM with heat exchanger to heat water in the hot water tank when motoring.The Tank holds about 5 gallons.
How long should it take to get hot water.I am on anchor at the moment and have been running the engine for 2hr a day (the air X marine went into melt down at the weekend in a 50knot gust) to keep the batteries charged but I am only getting luke warm water after 2 hrs.
Is this normal or is it possible the heat exchanger needs decoking.
The pipes to and from the exchanger see to be hot.

Andrew

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[vyv_cox]

Assuming that nothing has been changed, like swapping the hose connections over, then I suggest you might have an airlock inside the calorifier. With a bypass system like the one on the Yanmar it doesn't take much to stop the flow. My almost identical system is too hot to put your hands into within less than half an hour.

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[tome]

Unless you load the engine it will take a long time to heat up. I run the engine in gear against the warps for 20-30 mins to get piping hot water, but without the load it is lukewarm.

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[42_South]

On our Yanmar 3GM we have a 50 L tank located about 2meters away from the engine, but level with it.
Underway it takes about 10-15mins for a noticeable change in water temperature and then about 30 mins to fully heat - this appears to be quite fast and recovery is excellent after use of the hot water - it appears that the line from the engine must have an airlock or the fresh water circulation pump is gone.

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[snowleopard]

when you say 'heat exchanger', is it a fresh water cooled engine or is it specifically for heating the calorifer?

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[vyv_cox]

Can't be the fresh water circulation pump or the engine coolant would boil.

In cars, one of the first signs of a leaking cylinder head gasket is that the heater stops working. Calorifier would perform in exactly the same way. Might be worth a check that the head bolts are tight.

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