You are right and I do realize that but too many push and then pay.
When I started I did mine every 2 yrs or what worked out to be about 500 hrs.
I looked at the impeller and added a year each time. I now do the rebuild every 4-5 yrs and each time the impeller is still in good shape. and I look hard for ANY signs of excessive wear, excessive hardening and cracks/splits in the vanes. My yearly hours though have gone down.
A lot depends upon the pump, how fast it spins to move the needed water.
My engine has a physically large pump rotated at relatively low rpm and I do not run my engine hard so even fewer revs. The water it runs in is relatively cold compared to many areas.
Other engines use a smaller pump spun much faster and those will have a shorter rebuild time.
So no one can tell you a specific interval except as a guideline. But for new owners to a boat I would suggest at least yearly, then look at extending depending upon condition of the impeller.
That is also why I made the point about the suggested hours only as not great.
I thought that a blanket statement of 1,000 hrs was too long without the calendar time also. Things like impellers age regardless of use.
