Mercury 35/40HP 2 Cylinder Outboards Service Manual PN 90-42794--1, Page 134Get this manual
4Remove nylon washer (a), and seal (b) 6Remove impeller (a) and drive key (b) from drive shaftIf necessary use punch and hammer to drive impeller upward off drive shaftIn extreme instances, the impeller center hub must be split with chiselTake care not to damage drive shaft
5Inspect water pump for grooves; if grooved, replace insert
7Remove gaskets (a) and face plate (b)8Inspect face plate for groovesIf grooved, replace face plate