Why do I have so many raw water impeller failures?

[Rich Stidger]

Jerry, I agree the Speedseal Life is a great product and will protect an impeller from the heat and failure caused by friction with the cover plate BUT looking at Rich's photos I see none of the tell-tale heat stress cracking from that kind of failure. There do appear to be cracks at the base of each impeller blade, like it is flexing too much. Mystery to me. Maybe try those Globe urethane impellers...

Gunni- the light colored line on the vanes that you see is not a surface crack. I did bend the vanes back and forth to look for a crack and maybe that action caused the lines. The only vane that shows any damage is the one that broke off. There is the small vertical "nick" in each blade that I cannot explain at this time, but I don't see how that nick has anything to do with the vane that broke off. I will look at the Speedseal product. I thought that product was just a set of thumbscrews that promoted a faster impeller change. I didn't know that it somehow reduced friction too. And regarding the Globe impellers- MaineSail did a test on them 6-7 years ago and found them to be junk. I don't know anyone that uses them, and if they were as good as the claims, I would think equipment manufacturers would use them.

 

[Gunni]

Yeah, I saw that little divot in the vane edge, odd. Speedseal makes two products, one is just the cover plate with thumbscrews, but they also make Speedseal Life which is a remarkable improvement to the raw water pump. It installs a slip disk and effectively eliminates friction on the cover plate end of your impeller. The product claim is 10 minutes run dry performance. I do know that my impellers now come out each year in like-new condition. Speedseal Life might make the difference if your pump is having to pull dry suction from your thru-hull. I would also look at the mesh size on your strainer, and consider coarse mesh. Any reduction in fluid flow resistance is an improvement.

 

[boatertwo]

If the problem is water draining out after shutdown, then the installation of a ballcheck may keep it primed so it does not startup dry. Unfortunately, due to the height above the waterline there is no way to bleed air from the raw water system prior to startup, unless you install a vacuum system of some type to flood the pump before startup.

 

[Rich Stidger]

OK, I Googled SpeedSeal Life and read the reviews and watched the videos. That does look like an improvement over just a flat cover plate.

However, what about the inside edge of the impeller? The outside edge runs on a bearing but the inside edge still just runs on the pump housing. So this looks like half of a solution. I will grant that it is better, but won't the inside edge of the impeller heat up when run dry and still cause an impeller failure? If not, why not?