How does the impeller push the boat?

[Beachbummer]

On the seadoo pump there is a thrust washer and bearing, where the impeller pushes hard on the body of the pump, and the impeller stays inside the pump while the boat is pushed forward. The thrust washer and bearing hold the impeller from flying away.

As I'm looking at the diagram, I see a nut on the back of the pump, under the cone) Is the impeller and shaft held mostly by being pressed to the bearing? Does it push against a top at the intermediate bearing? Is this rear nut ever rubbing against the pump housing?

I'm missing the thrust washer, so I'm trying to figure out where that force ends up on the Yamaha.

Thanks!

 

[RedBarron55]

Normally a thrust washer will tale the load that is parallel to the shaft.
The bearing takes the axial loads.
If the thrust washer is missing then the clearance might be incorrect and the bearing could be seeing a different load than it was designed for.
The nut on the aft end would mostly keep the impeller on the shaft and the thrust from the jet would be pushing the impeller towards the front and the thrust washer would take this load.
Disclainer:
I am speaking in generalities since I have not looked at the drawings of the Seadoo.
In my opinion you should reinstall the thrust washer.

 

[Beachbummer]

Sorry, I had a seadoo before, but own Yamaha now, and looking now at my Yamaha, it did not have a thrust washer.

Hope that clears up my question.

Better stated... How come the Yamaha pump did not need a thrust washer??

 

[swatski]

Is the impeller and shaft held mostly by being pressed to the bearing? Does it push against a top at the intermediate bearing? Is this rear nut ever rubbing against the pump housing?

Interesting questions!
The way I understand it - it would be: no, no, and no.
The impeller is held onto the end of (long) shaft by left handed threads that tighten as the impeller spins freely inside the wear ring.
The impeller shaft pushes the coupler/transfer shaft and the crankshaft...
The intermediate bearing aligns the impeller shaft up (strait from the coupler, centered in the wear ring) and it's housing just seals the water off.
Right?

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[Beachbummer]

I think since there are some reduction gears in the intermediate housing, on mine, (old 230) the engine crankshaft does not line up with the crankshaft. This may be true for the 240 engine though.

If that where the boat is pushed, that's very interesting.


This is all curiosity on my part. In practice, the thing actually works, so it must make sense, but I would like to understand how things work if that's ever an option.

 

[Jgorm]

I think since there are some reduction gears in the intermediate housing, on mine, (old 230) the engine crankshaft does not line up with the crankshaft. This may be true for the 240 engine though.

If that where the boat is pushed, that's very interesting.


This is all curiosity on my part. In practice, the thing actually works, so it must make sense, but I would like to understand how things work if that's ever an option.

Yeah, there is a gear box attached to the end of the engine. That attaches to the impeller shaft coupler.
It looks like the front bearing takes the load with the spacer behind it.

 

[swatski]

It looks like the front bearing takes the load with the spacer behind it.

I don't think so.
I did forget about the gear reduction in MR-1s though. However, both "front" and "rear" bearings sit inside the stator/duct segment of the pump, behind (aft) the impeller. The impeller is attached to the shaft in front of those bearings. The impeller shaft than pushes the coupler and transfer shaft, with or without gear. I think, LOL.

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