mine --28 HP-- should be about 4.2 gallons per minute! This, according to some info on their site Engine Cooling > Support Centre > Jabsco-ITT.

http://www.jabsco.com/support/wizards/article-code-247.htm

"On average, petrol engines and fast running diesel engines require a raw water pump flow of approximately 8-8½gpm (36-39l) for each 100BHP for Direct Cooling systems and 14½-15½gpm (65-70l) for each 100BHP for Heat Exchanger Cooling systems. So, a 28HP engine (mine) being 28% smaller than 100HP engine, it should require 28% of that amount of water per minute...28% of 15 gpm is 4.2. (I measured a flow of 4.5 gpm from the exhaust, and from the pump --i.e., after the water had gone though the whole cooling system, and before.)

I'm really puzzled why similarly sized engines (like a 27HP Yanmar) should have specs that indicate they should move almost 50% more water at max. RPM than my engine does (in my bucket test). Totally puzzling to me...sort of contradicts the Jabsco info.

Too much data to sort through Too much thinking about this problem and not enough hands on!