Henry, on the PDQ 32 the 2GM20 Yanmars top at about 3600 rpm and the best fuel efficiency is around 2100 or 2200 I believe. I don't have any experience in the power cat. Of course, everything is dependent on props and weight, etc. Point being, that the engine's best efficiency may or may not be the boat's best efficiency. It seems to me that running a single at 2100 would consume less fuel per mile than running both at that speed, but maybe not? Maybe someone will do a test for us? Ed Schwerin