Bill Kiene wrote:
Hi All,

A fishing buddy has a 17.5' Crestliner walk through aluminum boat with a
Volvo 3.0 GS (4 cylinder 120 hp) I/O.

It goes 30 mph @ 4000 rpm and top speed is 39 mph.

What should his fuel consumption be for this boat while cruising @ 30 mph?

He is wondering if his boat is consuming more fuel than it should be.

Thanks for any help.

-
Bill Kiene

Kiene's Fly Shop
Sacramento, CA, USA

Web site: www.kiene.com


The two most efficient speeds for a planing hull are

1) the point at which it rises over the bow wave and is "on plane"
2) dead slow.

A wild guess is that your friend's boat might get roughly double the
nmpg at 30 that it realizes at 40. If you check the fuel consumption
chart for most engines, the curve gets extremely steep in the last
15-20% of the RPM range. If he's running at WOT to make that 40, he's
also spending a lot of money that's invisible (for now) on additional
maintenance and a premature rebuild.