Cheechako, I don't see any reason why not - if I'm not mistaken, the Perkins
4-108 in a previous boat
of mine had the hot water run off from the water pump
to the water heater. Having said that, its been a long time since I installed a new water heater, but as I recall
you may need to install a vented 'loop' between the diesel
and the heater in order to avoid air locks.