Re: How often do impellers need to be changed?
Most "professionals" will tell you to change your impeller every other year. If you run in particulary clean water, you could go MUCH longer than that. I had a Mercruiser Bravo series engine, so the pump is on the engine. I went 4 years and 400 hours in the amazingly sandy/muddy Illinois River before my impeller failed, 70 miles from "home" on a Sunday. But since it was a Bravo, no big deal, I could reach mine and changed it on the water. Volvo Pentas are even easier to reach than Bravos. However, if you have a Mercruiser Alpha, you can NOT change the impeller without hauling the boat out of the water. So if it fails, you are dead in the water. Hence the reason guys say to change them every other year. If you have an Alpha, and you change them every other year, don't be surprised if the one you take out doesn't look bad at all.
