Re: 1957 Evinrude 35hp water pump seal replacement
NO sealer on the plate mating surface. Some like to use a little dish soap on the impeller to make it slippery. Basically, install the impeller with the pin, then push the housing down over the impeller as you're turning the drive shaft in a clockwise direction. The impeller is actually pretty small, so you shouldn't have much of any problem.
Others may "fit" the impeller in the housing, then slide the assembly down over the pin. Either way works with this HP.
Also, remember a new o-ring at the top of the driveshaft with some molylube on the splines...but not the top.
Mas
Mas