'03 340 with 6.2L or 8.1

[jrcinnh]

does it have v-drive or sterndrive? With stern drives it may not be underpowered.

I tested a fully loaded 2007 340 with 8.1's and v-drives. It was OK but not overpowered. I wouldn't go any less.

 

[Hampton]

David,

You're right, it's not linear. My cruise at 3450 RPM is around 30 GPH. Without my log book, I can't say exactly for sure. That gives me about 27 MPH at 1/2 gas. It's just about my most efficient setting at 1/2 gas.

 

[dpmulvey]

Bigger displacement generally means more fuel at W.O.T.

But at cruise. . .. if one engine is spinning 4000rpm and the other is spinning 3600 RPM. . .That's a 10% difference; and nothing to sneaze at. Prop design is another huge factor.

I run 5.7LX's. W.O.T. on my boat is 4600 RPM. Cruise is 3000 RPM. My mechanic says never to run at 4000 RPM or higher for more than 60 seconds. His opinion (and I am inclined to agree) is that engine life is not linear with RPM.

If you have flowscans (or the like) it would be interesting to see what your GPH to MPG was @3500.