Impeller differences - where's volvo Paul??

[rosssavage]

TAMD 61A, impeller change time... Previously used genuine (££) Volvo impellers, this time gone for Johnson replacements. (pump is Johnson pump anyway...) the Volvo one has nine thick vanes, the Johnson 11 thinner ones. New impellers fit the housing correctly, the od of the vanes is the same and they seem to pump water effectively. Why the difference, and is it important? Cheers chaps!

 

[chrisharris]

I have just had to change the pumps on my TAMD71A's, the new pumps were fitted with multi-vane impellers similar to those you describe, the old ones had fewer, thicker vanes. I asked Jabsco about the difference they said the newer multi-vanes had very slightly higher (possibly more constant?) pressure, but the two types were interchangeable....

 

[rosssavage]

Thats why I like this forum - a perfectly concise and reasonable answer. Thank you very much, I can relax now and not fret about overheating next time I take the boat out.

 

[volvopaul]

The ones with more blades will pump slightly more water, they are just an upgrade, the blades are thinner to which may last longer.

They are also easier to fit,

Tip , when you buy, take the impeller out the box and squeeze the blades, if they are hard and not very flexible, reject it.

I recently tried to fit what was a new impeller in a d12, it was that hard it would not go in, even with a nylon tie around it.

Dont leave new impellers in your hot engine room either it makes them go hard.

 

[DAKA]

TAMD 61A, impeller change time... Previously used genuine (££) Volvo impellers, this time gone for Johnson replacements. (pump is Johnson pump anyway...) the Volvo one has nine thick vanes, the Johnson 11 thinner ones. New impellers fit the housing correctly, the od of the vanes is the same and they seem to pump water effectively. Why the difference, and is it important? Cheers chaps!

Volvo Penta impellers are usually nitile which is far more expensive.
It is harder and is durable under much higher temperatures, as far as I am aware the nitrile impeller is made by Jabsco.

Jabsco and johnson both make Nitrile and neoprene impellers.
Neoprene melts at a lower temperature but is much softer, easier to fit and lasts longer (in my experience) it also withstands oil.
If your new impeller is softer there is a good chance it is neoprene.

In theory the nitrile impeller will last longer should you experience a partial water flow reduction but they will both be wrecked if allowed to run dry.

Nitrile impellers can be submerged in boiling water for 1/4 hour before fitting, they stay soft for an hour or so.

In summary,
Neoprene impellers are cheaper , easier to fit, and last much longer in my experience than the Volvo Penta/cummins-mercruiser nitrile.