I know where a quality late model Freshwater A-4 is. Still in boat and in running condition. Great Lakes location. Let me know if you are interested and I will contact the owner. Obviously it is a drop in replacement for your existing engine and exponentially less expensive. When you retrofit with a diesel you have a myriad of costs in excess of the engine cost. New engine bed, new prop, new prop shaft, new control cables, new fuel lines, possibly a new a fuel tank, fuel filter, control panel etc.