Re: 1957 Marcury Mark 55 40 hp Lower unit Help

[jeff-register]

When you turn the shift shaft it moves a shift shaft in the gearset. It has a stepped shift shaft that has three different steps in the shaft. This forces the third shift shaft inside the prop shaft to move the shift dog on the splined shaft. There are three positions F, N, R, & on the Merc everything must be timed correctly in order to get all three. ALWAYS install with shifter & lower both in forward position to get it correct. You also have shock absorbers on your leg. That means the shift coupling has a rubber coushing. Be sure the coupling is good & not rotted as well.