what the difference in fuel consumption 5.7 to 4.3

[kovman]

I'm thinking about buying a 1999 21 foot bowrider with a 5.7 mercruiser engine. I really want a 4.3 but the price for this boat seems right in my price range. My question is what will be the basic difference in fuel consumption between the 5.7 and the 4.3 under general usage. I'm not looking for exact numbers. Will it be alot or basically the same on a same size boat. I've got two boys 13years old who are just starting to get into wakeboard and skiing. So, were not a heavily usage family.

 

[NHGuy]

Re: what the difference in fuel consumption 5.7 to 4.3

I'd say get the boat, a reasonable application of throttle will yield very acceptable fuel usage.
example: my boat's a little bit lighter than your candidate, but similar engine. I've had it for only 3 years. Got the ignition sorted out at the end of year one, got a correct propeller at the middle of year two and it has become really quite good on gas since then. Before I would run around at 3500 rpm with my 19 pitch prop just to stay above 25 MPH. I jumped to a 23 pitch and I go a lot faster with less fuel used. I also don't take off full throttle, just roll on some power easy. To get the best economy stay away from the last little bit of throttle before wide open. Wide open throttle is the most fun but it comes at a price.
Some on here claim that an over worked 4.3 and a conservatively operated 5.7 will get similar fuel usage, I can't say that I know. But when I want to run fast the 5.7 is handy.
Lastly it sounds good!

 

[Mischief Managed]

Re: what the difference in fuel consumption 5.7 to 4.3

There will be no appreciable difference in fuel consumption. It's not the size of the engine, it's the mass and hull design of the boat that determines fuel consumption. A boat like that is going to get 3 to 3.5 MPG at cruise, about 20% to 30% less at full throttle, and maybe 5-6 MPG at idle speed. Get the big engine.

 

[mnypitboat]

Re: what the difference in fuel consumption 5.7 to 4.3

There will be no appreciable difference in fuel consumption. It's not the size of the engine, it's the mass and hull design of the boat that determines fuel consumption. A boat like that is going to get 3 to 3.5 MPG at cruise, about 20% to 30% less at full throttle, and maybe 5-6 MPG at idle speed. Get the big engine.

I had a 5.7 carbed Mercruiser in my Q7, and my Dad had a 4.3 carbed Mercruiser in his Tahoe 215 deckboat. I actually used less fuel then he did on a trip, mixed idle and at speed. Now my MPI 5.0 in the new boat uses less fuel than either one.

Like mentioned, it is more how you use your throttle. We could get about 40mph all out in my Dad's boat, and we were using a ton of fuel, but my boat was barely working at 40mph.