sonic28

what is fuel efficency between the three. if i were to purchase a new boat forget the cost of the motors. is it 10gallons per hour diffrence or 20-30 ?and is there that much diffrence on total hp with twins?for example 37 active thunder 496s top end 70mph what about 500 hp 525hp

bobl

Fuel consumption(at cruise) is more a function of hull weight/design than engine size. A given boat will use about the same amount of fuel no matter what engine you get. Of course at WOT the more HP, the more fuel is burned. I would guess there's about 8 GPH difference between a 496 and a 525 at WOT, but I've never measured it. A single engine boat will use less fuel than the same boat with twins of equal power. You have less weight and less drag with a single engine(and less maintenance).

Raylar

There are two distinct things at work in boat efficiency. One is the efficiency of the hull and drive combination, including weight, hull form, CG, drive efficiency, prop efficiency, etc. This will vary from boat to boat and between same boat with different motors and drives. In motors the efficiency is really best measured by the BSFC numbers at various rpms and horsepower and torque levels. This is the "brake specific fuel consumption" and it is easily measured when dynoing various engines. It is really not possible to compare motors of different horsepowers and torques for this consumption number accross the board although it can be a good indicator of a motors overall efficiency. Each motor even of the same type will have different BSFC's depending on internals and setup. In general we find the new 8.1L- 496 when equipped with like efficient internals and setups, cubic inch for cubic inch will have a lower BSFC per horsepower than the older GEN 4,5,&6 big blocks due to better cylinder head design and electronic engine control and improved fuel control. As a rule though I would just assume that "BOAT" means "bring on another thousand" and not worry about the difference in fuel consumption unless you are running seriously long hours! In that case, get a diesel!