A nice weekend do nothing drive is to put a Merc 500 short shaft ski/fishing engine with custom speed prop on my restored Class F Chaparral hydro with that 3 gallon tank of gas and drive around at 55+ mph with terrific gas milage from the planning hydro, like about 1 hours worth. Testing Merc 3 Holer 2 carb engines though put things the other way around! The engines would burn the top cylinder way before that hour ever came close leaving you plently of gas in the tank instead! Boy those 3 Holer Merc/Mariner direct charged 2 carb engines are lemons! What were they thinking? Put a Merc 44 FE 4port, finger ported engine on it, now that is a cat of a very different color again!