Cost of fuel...

[Dave R]

Originally Posted by lakewinnie

I'm not sure how this equates to MPG, but I get around 5 GPH at 30 MPH in my 24 foot Four Winns bowrider with the 5.3 liter Volvo Penta. That seems to be the sweet spot.

Just divide the MPH by the GPH to get MPG. 30/5=6 so 6 MPG.

6MPG in a 24 foot bowrider seems pretty optimistic though.

Assuming you have a 300 HP 5.3, I'd expect the top speed to be close to 50 MPH. Since drag is a function of the square of speed we can calculate the HP needed to go 30MPH if the boat tops out at 50MPH

50x50=2500 2500/300=8.33
30x30=900 900/8.33 = 108 HP

It takes roughly .08GPH to make 1 HP so 108 HP would require 8.64 GPH so I think you are getting around 3.5 MPG, 30/8.64= 3.5