How do impellers work?

[paulgp6022]

I noticed alot of posters on here suggesting impeller replacement every 2 years or so. How come? Do they break or wear out quickly? What are they made from on Mercurys? How are they driven? Thanks for any info.

 

[paulgp6022]

Re: How do impellers work?

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[DJ]

Re: How do impellers work?

SS,<br /><br />They are positive displacement "vane type" pumps.<br /><br />They are generally made of a rubber compound. The rubber blades come in contact with the pump walls, thus they are always wearing. Even more so in silty or muddy water.<br /><br />In addition, any contaminates that run through the pump, such as sand, can destroy one in seconds.<br /><br />The impeller is "keyed" to the driveshaft and they nomally sit on top of the lower unit where it attaches to the exhaust housing. Since the driveshaft is turning anytime the engine is runnng, they are always pumping.

 

[paulgp6022]

Re: How do impellers work?

Thanks for the reply. I see now why it is always good to run the ear muffs before starting the motor out of water.

 

[roscoe]

Re: How do impellers work?

Because if they fail, you can overheat your engine and do very serious damage in very little time.<br /><br />They are made of rubber.<br />The rubber can get hard and take a set, or form to the shape of the pump housing. Then then don't work as well. They have to be able to flex and push against the outside of the housing. Why flex? Because the impeller is a round shaped paddle wheel, and the inside of the housing is oval. So to maintain contact with the outer wall, it has to flex.<br /><br />Also if the rubber dries out, or someone runs the motor without having the impeller in water, it can disintegrate or break chuncks out of it. Enough heat can be generated by running it dry, that adjacent plastic pieces can melt. The broke off chunks can plug up your water jacket, and further reduce the cooling.<br /><br />Also, sand and dirt can wear the rubber down.<br /><br />The actual impeller slides onto and is driven by the driveshaft.