I have this same engine in a H28.5, and it uses about .2 gals/hr at 2200 rpm in smooth conditions, .3 gals/hr with wind/ waves on the nose. It is a very efficient engine, but a lot depends on condition of the boat's bottom, the type of prop you have, rpms, and wind and wave conditions. Your boat displaces about 1,000 lbs more than mine. That said, I think you can expect to use about .3 - .4 gals/per hour in relatively smooth conditions. May be safe to plan on .5 g/hr.