Hello Lee,

I also have an Optima 4.7, although is it powered by 75 kW diesel engine.
The warm water boiler was an option at that time for the Optima and I believe (or pretty sure) that the "standard" option was to have it heated only by using the cooling fluid of the engine as heat exchanger. For sailing boats this is a very common setup (Dehler!). This will ensure hot water for about 24 hours as long as you have been operating the engine. The boiler is filled by the water pump from the fresh water tank. So after a while at a campsite you will not have hot water anymore. A solution is to install a 220V heating element which can be used to warm the boiler when stationary. I have done this by installing an Elgena boiler (10L) with heating element (220V/ 600 W) combined with heating by engine cooling fluid.

Please take care that you empty the boiler, and the entire water system, in freeezing temperatures, otherwise you'll freeze and blow up your boiler.

I'm not aware that a Truma heating was an original heater for a Dehler Optima. Mine came equipped with an Eberspaecher heating (D3L I believe).

Have fun with your Optima

rgrds, Bert