1998 90hp Mercury Prop spins in neutral

by Paul
(Massapequa, ny )

I recently serviced my lower unit including water pump on my 1998 90hp merc. When I went to put it back on couldn’t get the boat in reverse took it back down and did it again making sure to line up the small spline at the bottom back of the lower unit behind the water pump housing with the spline in the bottom of the cowling. After the reinstall the shifting was very easy in forward and reverse but I notice now my prop spins in neutral. Never noticed that before but maybe it always did before I splash the boat from dry dock do I have a problem from the install that I didn’t catch.

Thanks for the help