My CL Luders 36 has a Westerbeke four 107. With 107 cubic inches it can produce up to 40 HP @ 3,000 RPM and would burn 1.3 gph. A more useful setting is 2,000 - 2,250 rpm making a bit under 20 HP and using about .7 gph.
I think the transmission ratio is 1:91 to 1 but am not certain. The propulsion system ends on a three blade prop, the pitch of which is presently unknown.