Fuel consumption: 4.3 vs 5.7 vs 7.4

[ZmOz]

I am leaning towards buying a 16-19 foot sterndrive. I don't ski or fish, I like to drive around fast. This obviously uses ALOT of gas. I'm giving serious thought to running the inboard on propane. I will be modifying whatever type of motor I get to be around 300hp. Given the same HP, is there going to be a big difference in fuel consumption between a 4.3 V6, 5.7 V8, and a 7.4 V8? How much of a difference?

 

[Bondo]

Re: Fuel consumption: 4.3 vs 5.7 vs 7.4

Well,<br />The 4.3l will Never see 300hp.......<br />Not in a Usable rpm range.......<br /><br />The 5.7l will be lumbering along.......<br />And,<br />I've Never Seen a Big Block, That Didn't Drink Alot Heavier than a Small Block...........<br />Even when it's Not Even Breaking a Sweat.........

 

[ZmOz]

Re: Fuel consumption: 4.3 vs 5.7 vs 7.4

It wouldn't be hard to get 300hp from a 4.3 with a turbocharger or supercharger.

 

[Bondo]

Re: Fuel consumption: 4.3 vs 5.7 vs 7.4

True..........<br /><br />She'd Still be Straining though......

 

[TwoBallScrewBall]

Re: Fuel consumption: 4.3 vs 5.7 vs 7.4

When I had my S-10 with the 4.3, I had found a source for a stroked and overbored 4.3 long block (4.5 I think it was) that made 300HP naturally aspirated, about 425 with a modest compresser on in. Can't find the link now, but it can definitely be done! <br /><br />Fuel usage is bacically a function of both horsepower and displacement. 300HP out of anything is going to use a lot of gas.<br /><br />The main difference will be engine stress. The 4.3 will be pusing hard to hit 300hp, where the small block will be working less and the big block will be asking for more gas...

 

[mkast]

Re: Fuel consumption: 4.3 vs 5.7 vs 7.4

http://www.boatingmag.com/article.asp?print_page=y&section_id=8&article_id=483&page_number=1 <br />Copy and paste<br />Read this article, very informative.

 

[MrDumb]

Re: Fuel consumption: 4.3 vs 5.7 vs 7.4

They will all get the same MPG when they are off!!!

 

[Schmoe]

Re: Fuel consumption: 4.3 vs 5.7 vs 7.4

If your wanting about 300 HP, make sure you don't go with the Alpha drive, you'll need a Bravo. Sure the Alpha's are rated up to 300, but I've seen many of the strip the gears around 275 hp.

 

[vinney]

Re: Fuel consumption: 4.3 vs 5.7 vs 7.4

They make a heavy duty gear set for the alpha. You can put more than 300 hp to them. We used to have a couple guys that ran the 250 puffer on the small block. We took the drive apart every year for inspection and reshimmed them every year. None of the hp gear set ever had failure. Mercruiser made them in 1997 when they put a big block behind an alpha.

 

[ZmOz]

Re: Fuel consumption: 4.3 vs 5.7 vs 7.4

How much of a difference in MPG do you guys think there would be between the 350 and a 454 in the same boat, with the same HP?

 

[DHPMARINE]

Re: Fuel consumption: 4.3 vs 5.7 vs 7.4

ZmOz,I think you should think of the engine as a pump.Air goes in and gets pumped out.Now the larger the piston (or displacement) the larger the pump.More air....more fuel...<br /> DHP