Make sure if running twins that they are in sync.

Find your boats sweet spot. On most planeing hulls idle speed is probably most
efficient but if I wanted to go that slow I would have purchased a sailboat.

On my boat for example the "sweet spot" is 3100 RPM with the drives trimmed
slightly up. This gets me, depending on conditions anywhere from 28 to 30 MPH
and a fuel burn of just under 11 GPH. Of course wind, load and currents can
affect this but these are my averages over 5 seasons of usage.

BTW, gasoline at my marina is $2.339 for 89 octane, on the street anywhere from
$1.999 to $2.299 for 87 octane. Not to shabby. Other marinas are charging from
$2.45 to $2.75 per gallon. My marina and the other marina in my harbor have
always been lower than the norm for some reason. Maybe that is why both are
full.