the water pump
impeller you're talking about is a small belt driven unit, close the seacock supplying water
, there's 3 screws that hold the cover on. grease the impeller lightly with some silicone grease, replace the gasket
with a new one when buttoning up the unit. you should have 2 fuel
filters, one small paper one in the fuel
bowl that feeds the injectors and another at a fuel water separator. both simple to change. there's a number of threads here on doing this. you might check the last time the valves were adjusted. another simple job, I think the adjustment interval is 500 hours. Again, there's a few good threads here. Btw, not all the engines have the internal zincs.