diesel
Some additional notes and also owning a C hawk as well as several other center consoles as well as downeasters I'm speaking from experience; consider this with regards to engines in lieu of the fact that you're primarily a sportfishermen I would research the cummins and I'll tell you why, mainly increased weight and space required for the installation, I would look at yanmar do your homework and you'll probably save over 900 lbs without the gear. Also because of the RPM'S you'll be swinging a smaller wheel, so weight reduction and speed derived from that another factor. Someting to consider when you are adding weight to an existing medium to low shear boat that can be a bit wet. You say that you average 2 mpg at what speed?, as we speak gas compared to diesel is cheaper, I would explore some other ways to improve performance perhaps tabs, prop modifications of which there are some new inovations, discuss lifting rails ,is the engine on a bracket, stretching your hull with a high transom and bracket could dramatically improve the efficency and ride something you need to explore. So it's an important decision but non the less an interesting one. The reality is that a 300 HP engine may be more economical but in my opiniom not all that much, even if you double your mpg it's a long way to regroup your investment. C hawks a great boat that whole NC area is home to many spinoffs, C hawk, Privateer, Parker, Maycraft all semi hybrid workboats not a helluva a lot of bottom on any of them but for the most part their 25 knot boats in most conditions. Downeaster was also out of Marshallberg I think Lookout took the remaing molds that was also a nice "carolina flare" type boat too.And last but not least compare maintenance oil changes, filters, engine zincs and so on.