Installing Hot Water Tank Heat Exchanger

[Noreastern]

We are installing an Isotherm hot water tank and heat exchanger that uses the cooling water">engine cooling water to heat the tank water. Our problem is the only place to mount the Isotherm unit is above the engine. We have a fresh water cooled 3GM30 Yanmar and we were planning to use the fresh water side of the engine to heat the hot water in the Isotherm unit. But being that the tank is mounted higher then engine I see no way of filling the engine cooling system. Isotherm recommends a vented loop and I see how this could prevent back flow but not how to fill system.

Any help would be appreciated.

[belizesailor]

I don't see how you could ever fill the cooling system with the water heater above the highest point in the engine's cooling system (the fill cap on the engine's heat exchanger). Maybe by mounting a second fill tank above the hot water heater?

And if you somehow did manage to fill the system, then if you open the engine's cooling system fill cap, the coolant above that level is going to flow down and over flow out the neck.