Sea Water Pump Impellers - Why not silicone?

[Dettom]

I've always wondered this. Every year, while replacing the sea water pump, why does someone not manufacture the impeller out of high temp silicone rather than rubber? Seems like it would stand up to wear much better than rubber which tends to get brittle over time. Then the blades start breaking off, leaving pieces of them in your oil cooler to have to back flush out of there.
Also, I think it would stand up better to the occasional dry start too. Every once in awhile, I see guys haul their stern drive boats out to the ramp and start them as their wife is backing in to the water, then I'll see the same guys, run the boat on the ramp after the drive is out of the water, thinking they're flushing out the motor. Makes me cringe. Any one have any inside knowledge? Should I start practicing for a segment on Shark Tank?

 

[TX Foilhead]

A company called Globe makes a run dry impeller, I've heard mixed reviews about them. The problem seems to be they don't cool as well at some RPM's so they work well for some but not for others.

 

[FreeBird236]

A company called Globe makes a run dry impeller, I've heard mixed reviews about them. The problem seems to be they don't cool as well at some RPM's so they work well for some but not for others.

I was told also for some reason they don't always prime.

 

[Shortdeck]

A company called Globe makes a run dry impeller, I've heard mixed reviews about them. The problem seems to be they don't cool as well at some RPM's so they work well for some but not for others.

Running dry won't keep the alarm from sounding. It will trigger a low water pressure alarm.

 

[Dettom]

A company called Globe makes a run dry impeller, I've heard mixed reviews about them. The problem seems to be they don't cool as well at some RPM's so they work well for some but not for others.

I looked up Globe on some other boating forums, mostly sailboat guys and the reviews were "Ehh"..But in some of the pics, the vanes were cracked but the pump housings looked nothing like what I've seen before. Almost a D-shape inside. They're supposed to be able to run dry for 15 minutes, not that I'd try. I would think some chemical engineer would be able to perfect it . Paging Walter White.

 

[boatdoc55]

There was a company many, many moons ago named "Barco". They had this idea also and I changed out a lot of the small Volvo Penta impellers with them. There failure rate was miserable and we ended up back to OEM impellers. They were blue in color and it seemed to be a good idea at the time. Thank God we didn't loose an engine. The company did buy them all back.

 

[mjc]

I screwed up last time out and ran mine at the ramp with the water valve shut. After the alarm went off I checked it and my sea strainer was dry. Went to paul65k's slip to check it. Opened the valve and it checked out OK with 12 psi running. I have a stainless pump housing so maybe the smooth finish helped it survive.

 

[getreal]

The "dry run" impellers are not offset as much as stock (closer to centerline), that's why they don't pump as much.