antifreeze

I bought my 1990 Hunter 28 ten years ago last month, and during that time I never had hot water that came from the heat of the engine because the valve next to the heater had meet turned off. I opened it and of course it started leaking so I replaced it and I now have hot water. That was two...

I am planning to change antifreeze in the cooling system of my Yanmar 3YM30 (the closed circulation, not the sea water). I could find in the engine manual the coolant capacity, but that does not include the volume of the coolant circulating through the water heater. Does anybody know what extra...