Water pumps on outboard driven cats

[Sparx]

Just finishing a routine haulout of my Maine Cat 38. The haulout was primarily for fresh bottom paint, but of course is an opportunity to inspect everything and do preventative maintenance.

My habit is to change out the water pump impellers of the two Yamaha T9.9s engines, this being easy to do while the boat is on the hard. After 300 plus hours the water pump impellers and housings were pristine, showing little or no wear. At the previous haulout I observed similarly little to no wear with more than 500 hours on each engine.

For discussion, how frequently to you change the water pumps on your outboard powered catamaran...

It is looking like 500 hours or more is possible. So far for me changing these water pumps is easy and not expensive insurance that I will likely continue at each haulout.