Quicksilver offers 100% genuine OEM gearcases for many Mercury and Mariner applications between 40-300 HP. These are genuine original factory parts. Invest wisely in your time on the water with a Quicksilver gearcase, because everything is riding on it.. Black, 2.3:1 gear ratio. 20" long shaft length. 12 pinion teeth.. Fits:. Mercury 75-125 hp. 2-cycle outboards with 6 jaw reverse clutch