On Tuesday, March 4, 2008 at 6:58:00 PM UTC-5, wrote:
Hello all,
I have just purchased an older Starcraft 18' runabout that
currently has a 120hp 4cyl Merc gas engine coupled to a series 120
Merc I/O drive. I intend to convert this package, using the I/O, to
diesel using a 52hp 1.6L VW diesel engine in place of the merc 4 cyl.
Due to the relative unavailability (and cost) of a wet exhaust, I
intend to use a dry stack, and run the diesel with a radiator normally
found in the VW vehicles...side mounted and all tucked into a rear
engine box
that will be manufactured to allow adequate breathing and heat
dissipation. My question is regarding the pump system in the I/
O...can I just remove the impeller, or should I direct its output into
an open circuit back into the bay? Does the pump in the I/O have any
cooling or lubricating capacity for the unit?
This project is intended to provide for a work boat used in Coos Bay,
Oregon, for non commercial fishing and crabbing. Reliability and
economy of use are considerations.

what about the omc method ? using the impeller to pump water into a heat exchanger made like a pipe with tubes running through it. still have water pump and use antifreeze.as far as exhaust go`s make a triple wall pipe setup like you use on fire places, just smaller. i made one out of pipe and insulation before.