The 763758 pump with the plastic housing and small impeller was introduced as standard equipment in the last year of production of OMC’s six horse motor in 1979. The later six horse motors are of a different design and use a different style water pump.
The great news is the newer 763758 pump kit is a straight drop in replacement kit for any ’54 – ’79 OMC built 5.5, 6 or 7.5 horsepower motor. The mid-sixties five horse motors used a different gearcase so this pump kit wont work with them.
