Re: fuel usage 4.3L
It is quite an open question and even if are quite specific on details, the answer can still vary. <br /><br />Data for your ballpark guess. In my 23ft Bayliner Trophy, 5.7L Merc, 50gal on board, 3 people, minimal gear, I get about 1.8 miles/gal at 28mph (not knots), this is 15 gals per hour. Range with a full tank of 95gal is 171 miles - best case.<br /><br />Go with Bondo's suggestion, give it everything you got, with split tanks, you can position them into the odd spaces to gain more.<br /><br />An underpowered boat can burn more fuel than one with an overpowereed (not extremely overpowered) boat for reasons of not being able to achieve optimum plane or taking a long time to get onto plane. The drag is extremely high during the hump getting onto plane. <br /><br />I have come across an owner claiming significantly better fuel consumption after replacing their 150hp outboards with a 200hp. With 2 strokes, the losses from a larger engine are even higher, yet he still achieved better mileage. With 4 strokes it will be better.<br /><br />Hull size/shape/weight/weight distribution/cruising speed have much much greater effect than the engine. Cruising speed is the user controllable item and has the greatest effect. Mathematically, it varies as a square of speed. You get about 4 times the fuel burn if you double the speed and 16 times for a 4 fold increase in speed (all are on plane conditions)<br /><br />An engine on the bench with no load only needs to overcome its own friction and losses, bigger the engine larger the losses and equates to poorer performance by bigger engines. Not so when running under load.<br /><br />Between an adquately powered boat and an overpowered boat, the overpowered boat will be worse. Between an underpowered boat and overpowered boat, the underpowered boat is worse.
