I have a 2003 90HP Mercury saltwater and have been advised to put a new water pump in before it breaks. Is this valid advice?
Yep. Its sound advice. The nitrile rubber from which the impeller is made breaks down with time. Add in the abrasion from sand and grit in solution in the water and they degrade even further. Actually kick up mud or sand once in a while,and the wear plate and other parts really star start to go. Its cheap insurance and in general, I recommend changing the pump at least every two years--annually if you run aground.