The effects last much longer than that. I've gone back into motors months later, and the impeller is still "slick" compared to when they are brand new and "dry". I think the grease impregnates the surfaces, kind of like when you season a cast iron pan, if you are familiar with that reference. It definitely increases service life.

The service manual specifies "waterproof marine grease". Vaseline is a nice, clean grease, and seems to have good resistance to water, so I'd guess that would work okay.

You generally don't want to use silicone on a water pump, unless you are compensating for a heavily corroded surface below the baseplate, and in that case, I would recommend using Permatex non-hardening sealer under a new gasket. The grease does not affect that bond in either case.

There are often many ways to do things, but we stick with methods that give the best results for the customers, and most of the time that means sticking with what the manufacturer recommends. Our business is all word of mouth reference, and we stay very busy. But please understand that no insult to anyone else is intended.

-TH