First off keep in mind I've never even seen your particular type engine
but after looking at the exploded parts
diagram it would seem you can buy most of the wear items and rebuild
the pump. I am assuming that your engine is freshwater cooled and that the impeller is still usable. I would be leery of an impeller type pump running in hot water
and also the thermostat when closed would restrict the flow too much for the impeller. An electric
centrifugal pomp would most probably do the job just fine. I can't remember the manufacturer's name but they are used in buses and motor
homes to circulate hot water
from the engine to the heaters in the back of the bus. Good luck. Just my two cents, Mike.