Rubber button with raw water impeller

[Rich Stidger]

I just replaced my impeller for my Volvo MD22L-B. I had put in a new pump about 16 months ago and with 227 hours on the pump I figured I should change it. I'm on a Maine cruise and I expect many more hours of motoring if the past two weeks is any indication.

Anyway, the pump had a Jabsco impeller installed from the factory and this impeller has a rubber plug that fits in the hole over the shaft. See the picture for this plug installed. This picture is from a while ago and is not my current replacement.

Anyway, the replacement impeller I installed is a Johnson brand and it did not come with a rubber plug. I remember that other impeller changes did not have the plug either but I don't remember what brand they were.

So I installed the plug from the original impeller into the new Johnson impeller. It was a struggle because the plug kept popping out before I could get the gasket and cover secured. But I finally had success.

So I am wondering- what is the purpose of this plug, and why did my Jabsco impeller have one while the equivalent Johnson did not?

And most important- Is this plug necessary?

 

[Benny17441]

I would suspect it is something Jabsco may have re-enginereed around. Are their hubs more supceptible to leave marks or make grooves on the pump cover?

 

[Rich Stidger]

The hub on both the Jabsco and Johnson look the same- they are recessed a good 0.1" from the edge of the impeller.

 

[relentless lily]

I`m still new to this but when I put a new impeller in mine the new one had threads inside the end. They were so you can thread in a puller to easily remove the impeller. Perhaps the cover was to keep the threads clean if you had this type. Mine did not come with a cover.

 

[Rich Stidger]

Here is a better picture

This is a brand new Jabsco impeller with a new button in the package. The Johnson impeller that I installed looks exactly the same except there is no new rubber button.

The button is pressed into the end of the impeller after it is installed and before the cover is attached.

Both the Jabsco and the Johnson impellers are the correct ones for my pump.

So my question for the experts remains- What function does this button provide and is it necessary? I suppose I could ask Jabsco why they provide a button but I figured somebody here would know the answer.

 

[Benny17441]

Maybe it is the fancy model with "hubcaps"? Rich I gather that cap is not water proof so corrosion prevention would not be a reason. When you do find out, please let us know.