Impeller fails to pump water.

[Soddy]

We put a new impeller in our 94 Johnson 20 hp motor. When we tried to start the motor no water flowed from the overflow tube. We had cleared a small obstruction in it before start up. We removed the lower gear case unit and as done in a Youtube video we turned the drive shaft with an electric drill after submerging the lower unit in water to the cavitation plate. No water came out the water tube gromet. We suspected the key in the impeller was worn out. We then removed the impeller from the housing, put the key in place and lowered the impeller to engage the key. we were now able to turn the shaft by turning the impeller and also turned the impeller by turning the shaft. This indicated the key was still functioning. yet we could not pump water. We would appreciate if anyone has an explanation for this situation. Any suggestions would be appreciated. Thanks

 

[oldboat1]

don't understand -- couldn't pump water while the l.u. was still removed? Is the assembly complete -- cup/O-ring/housing? also plate/gasket/seal underneath the impeller? Kind of a complex assembly....

 

[Soddy]

Thanks oldboat1.The assembly was as we found it when we pulled down the lower unit. I cannot understand why the impeller did not pump water when we immersed the lower uni and ran the shaft with the electric drill. A licensed mechanic looked at the impeller and housing. He said we did not need a repair kit.
There was no gasket seal under the impeller, just the plate.

 

[jakedaawg]

If you are trying to spin this with a drill motor, don't. Your more likely to mess up splines than to verify any thing.

While the lower is off you might back flush in the t-stat housing and out the water tube. Then assemble the H2O pump on the lower, reinstall, verify good cooling by running in a deep tub. I use a half of a plastic 55 gallon drum. Running on muffs tells little.

 

[oldboat1]

Check it against a diagram: http://www.iboats.com/Gearcase/dm/ca...iew_id.1537725 If it's not fully sealed, it would presumably draw air, and fail to move water. I see a gasket under the plate, and a seal under the housing/cup (model shown, anyway).

 

[flyingscott]

Is this an aftermarket impeller?

 

[OptsyEagle]

Also, when you said that you submerged the lower unit in water, did you submerge it so that the water level was above the water pump or just above the intake holes of the lower unit? Since these water pumps are not self priming they need to be fully submerged in the water to work properly.

 

[Soddy]

jakedaawg. What and where is the t-stat housing? oldboat; Thanks for the diagram. I was able to print it. I am going to order a pump repair kit as listed on BRP catalog. flying scott: I do not know if it is after market; will check when I go to my marine dealer Thanks all

 

[Chinewalker]

The pump itself must be submerged to start pumping. They are not self priming. Water level to the AV plate isn't going to do it...

 

[clemsonfor]

If your confident it's toGeather and not worn why not just put it togeather and put water midway up the midsection submerged in water and run it. All this deliberation you can have the lower back on. If you are sure it's right it will work I bet when bavk on the boat and installed and proper water level as when on boat running

 

[Derrick Fronckowiak]

Just an after thought here. When you ran the drill on the drive shaft, did you run it in the right direction?