Mercruiser 5.7ltr V8

[dalton565]

Hey guys

im looking at a boat (fletcher 20ft speedboat) 1999 that has this engine installed on it.

The guy tells me that 10 gallons of fuel lasted him 6 hours, and that was skiing and pulling tubes.

I recon this is a load of rubbish hes pulling my leg. Can anyone shed an idea on what its more likely to be like.

Im thinking hes trying to get rid of it with the recent hike in fuel costs. What do ya'll think ?

 

[QC]

Re: Mercruiser 5.7ltr V8

You'll average 8 - 10 gallons an hour with that setup . . . 20+ at WOT. Go here for more data: Boat Test dot Com Browse around for some other examples, but this is a carbed 5.7L. That Fletcher will probably be faster, so move the speeds up a little vs. fuel, but the fuel curve will be very consistent with RPM. Prop load "curves" are very linear, so the load goes up with RPM as does the fuel use in a relatively straight line. The exception is when you jam the throttle to get up on plane and that point will show a rise in fuel use vs. RPM and then it will flatten out again. Almost every one of these carbed small block V8s get pretty close to the numbers above.

 

[dalton565]

Re: Mercruiser 5.7ltr V8

thanks
new the guy was talking out of his backside

 

[Silvertip]

Re: Mercruiser 5.7ltr V8

Possibly not! 10 gallons in six hours is a rather meaningless number since we have no idea how much of that time was idling, getting skiers ready, loading tubes, and how long the runs were.

 

[45Auto]

Re: Mercruiser 5.7ltr V8

Yeah, some people want to divide their TOTAL time on the water by the amount of fuel used to determine their gallons/hour. Unfortunately, the most common usage is that gallons/hour is measured with the engine running!!!! It's usually pretty obvious. As QC and Silvertip said, only way 10 gallons lasted him 6 hours was if he spent 4 or 5 of them at anchor.

 

[QC]

Re: Mercruiser 5.7ltr V8

I agree, Silvertip, and had the same thought, but I took the post literally.

 

[tmh]

Re: Mercruiser 5.7ltr V8

dalton, what's it matter? I wouldn't "call" the guy on a lie .....he's not pretending his V8 has any magic fuel saver on it, just giving somewhat incomplete anecdotal evidence. Maybe he eats lunch, listens to the radio, etc. during this 6 hours. Like others said, he's sure not whipping a tube around all that time. We use 10-15 gallons for a day on the lake tubing with the same engine.....and yes, we're only really tubing a small part of that....how many rides does each kid need?

It sounds like a perfect engine for that boat so i wouldn't complain about it - it's what you should want. A 4.3 MPI MIGHT be Ok for that boat also, but the fuel savings are a drop n the bucket between the two engines in the big scheme of boat ownership costs. The 5.7 will have more power when needed and some more top end also.