When you service your water pump, do you replace everything (a kit), or do you just replace the impeller? Thanks.

 I personally do a kit, along with a thermostat, if it has it a poppet valve, I replace it too. 
I had an overheat alarm going off, I replaced them again, still had the the alarm buzzer still. Found out I had a poppet valve, it opens as a secondary thermostat. Problem solved.

Some don’t have them, might want to check it out.

My local boat shop does mine. They do the kit and anything else that might need changing, Yes I do trust them.

From hard learned experience, when you do replace your impeller make sure to remove all of its pieces if it comes apart.

 

I do my own impeller replacements, and one time a small piece of it was pushed by water force up into the tube going to motor and it blocked cooling water to the engine.

 

I had to take it all back apart and do it twice just to clear the tube with air pressure from top side.

 

As to your question, I'd say it depends on the motor. With my old 1987 OMC Evinrude all I need to replace most of the time is just the impeller, but have had worn impeller housing needing to be replaced so inspect thoroughly. A kit may not be needed every time.

Depends on the water quality sediment etc and how often the impeller is changed. Annually if the housing is in good condition the impeller only.

2 or 3 years or the water pressure is pulsing use a kit.

Tom

I have always had a tech do mine.  They do it every 3 years.

I run water through the impeller once per month in the off season and by doing so, can go 5 years.

Certainly not saying that you shouldn't follow manufacturer recommendations but the 3 year recommendation is for worst case scenario........salt water, stained water with sediment.

Impellers dry out and crack when sitting for long periods.

I'll look at the housing and if there's wear or grooves I'll buy a kit, if not just the impeller.

If I've got it opened up I install the entire kit, even if everything looks good.