ThirdBird, thanks for confirming my thoughts regarding O2 sensors.

Oh yea, I agree, if there wouldn't be much to gain, why mess with it? Although, if the engine compartment was holding in a lot of heat from the engines, on paper there appears to be some power that may be felt in the pants.

Using the air density ratio equation [D.R. = (T1+460)/(T2+460)], say you could reduce the air temp going into the engines from 110°F to 90°F on the same day with better ventilation. D.R. = (110+460)/(90+460) = 570/550 = 1.036, or a 3.6% gain in power due to the cooler, more dense air. In my case with twin 320HP engines, that should be around 23HP. Not a whole lot, but maybe worth it(?)

I know going from the hot, humid summer to cool, dry fall days, my rig is consistently 2 mph faster. But that is more than a 20°F change!:drink: