At 550 hours I thought it best to have my two BF40 honda water pump impellers changed while doing some other end of the season maintenance. All of those hours were spent on the muddy Mississippi so lets just say less than ideal conditions. The indicator steams were noticeably weaker but I keep a close watch on them and have never had an overheating incident. After seeing the old parts I was relieved of some of my guilt. There was very little wear on them but they had a definite curve, or set, to the blades that decreased their efficiency. The knobs on the ends of the blades were like new. I am not bragging about my maintenance avoiding but did want to set some kind of bench mark for water pump life expectancy. Both motor's impellers were in the exact same condition so I rule out just being lucky. If you knew me you could have ruled out being lucky long ago.