1997 Johnson HP fuel consumption is high

[PickyBiker]

I bought a used boat with a 1997 Johnson 4-cyl 90 HP motor. It seems to consume fuel faster than I would have thought. It consumes about 4 gallons of fuel after only an hour of cruising at 3000 rpm.

Is this typical? Is there a way to accurately measure MPG GPH on these engines. It is only pushing a Fiberglas avenger 15' 4" bass boat.

Thanks!

[boats.net]

They do like gas. Check spark plugs to see if burning rich or normal.