fuel economy

[dlb511]

A question for you all. I have worked boats , sold boats, and owned boats, but not for many years. Right now I am starting retirement and hope to find a nice classic center console to use. My question is: All things equal; 20 ft., center console, similar performance, Which would be the most economical on fuel: I/O, outboard, or straight inboard? Any recommendations? Another issue is that I cannot afford the cost of a new power plant, no matter what type. I am looking for a Classic Seacraft, Mako, or even a Shamrock. In other words a saltwater fishing boat with some offshore capability. From your experience, which would prove to be the most economical over the long haul? TIA.