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How often do I need to replace the impellers on my raw water pumps? I had them replaced last winter and I have put just under 20 hours on the engines since then.

Thanks,

Peter

If you have not run them dry, you will be ok for next year. If you put any type of heavy hours on the boat, depending on the hours I would tend to change them at a minimum every two years and if you go really heavy then every year. If you keep it to 50 hours and under you can go a little longer. I used to watch the water flow out the exhaust when running and also the temp of the engines. Once I saw the temps getting a little high or the flow of water out the exhaust looking a little weak from when they were new, I would change the impeller. If you ever find a piece missing you need to go hunting for it. Usually winds up in the transmission cooler.

Once you do it once you will find it is not that hard. The Port engine should be easy since the pump should be right there by the companionway. The Starboard gets a little tight. I would remove the Starboard wing to give yourself more room, but I somehow always found myself hanging over the engine looking down trying to remove the pump. Once the pump is off, changing the impeller is a piece of cake.

I find they last a really long time if you don't damage them by running dry or picking up debris. My last set I changed at 650 hours, the set before that around 500--both sets where pumping fine when replaced. The impellers showed a lot of wear, but still pushed plenty of water.

Tony Meola wrote:If you ever find a piece missing you need to go hunting for it. Usually winds up in the transmission cooler.

Once the pump is off, changing the impeller is a piece of cake.

I think these are very good points. Impellers are not expensive and I never wanted to be the guy bragging about how I changed one in under 2 hours while at sea... My Crusader 454s take this kit https://www.marinepartssource.com/thru- ... 10615k-shw I'm not sure if it a result of wear or my pumps have a slightly different back plate than standard but I have not found a good seal with the supplied o-ring. I was advised and have run a bead of silicone in the channel the o-ring sits in and that has worked well for me. It's a pain to clean out next time but it works.
You will find significantly more expensive impeller kits that also contain bearings. I have always just spun the pump axle by hand and listened for any grinding. I am told and believe that over tensoning the belt will accelerate bearing failure. I have run my pumps with a minimum of play in the belt and have not (yet?) had any issues with bearings.
I have run impellers for multiple seasons but don't recommend that if possible.
Good luck and enjoy those 454s.
Stephan