I have put on a spread sheet and graphed both gasoline twin 454 Mercs, a single
and twin Yanmar
Diesels, all on planing fishing
Without exception the more RPM
, the more the fuel
burn, actually the less mileage. I had Fuel flow meters and graphed fuel flow vs speed.
There were a couple of steep slopes on the graph, like you donít want to run right just before when she gets onto plane, bow high and rolling a huge wake or full throttle, lots more fuel, little additional speed.
But surprisingly there was no sweet spot, nowhere where fuel mileage actually improved over the lower throttle setting, I was sure that right where she breaks onto plane would be a sweet spot, but it wasnít.
As I said there were places where the graph steepened where increased RPM
gained very little speed, but at no time did it ever crest and come down.
However in all three cases speed just as she broke onto plane was the most pleasant, least noise
, felt like you were getting somewhere without pulling the guts out of the engines.