Promise was powered originally by a raw water cooled Volvo MD-17C (35hp), Walters Vee drive and 2 blade LH prop. Some Vancouver 36s had the 2 cylinder MD2/MD11. I was concerned that the Yanmar 3GM at 24-27hp was a little on the underpowered side. As it turned out, the boat performed better with the Yanmar than it did with the Volvo even when the Volvo was in tip-top shape (not often).
The 3 blade prop improved slow speed maneuvering although I had to relearn how Promise backed with the now RH prop.
Here is flat water speed data with a clean bottom and prop:
The difference in weight between the Yanmar and Volvo required a ballast change . The relocation of 100 of the 200 ft of anchor chain to the laz helped. There is plenty of room for an ingot or two of lead in the engine room.
Of course there will be days when trying to bash into a head wind and sea you wish you had more horses but try to remember you are a sailboat.
George and the MD-17C (an ironic side story):
When I bought Promise I had the engine and power train surveyed. The report stated that everything was in great shape except the surveyor recommended that the stainless steel aqualift be replaced. In the next 5 years just about everything failed including a complete loss of oil pressure off Naples Italy and a lock up of the transmission in the Belgian canals. The engine and transmission were replaced when Promise returned to the Chesapeake. Hoses, wires, etc. all needed replacement. All except- you guessed it- the stainless steel aqualift.