1998 Sea Doo GTX jet pump does not pump water above idle speed

[jbunceseadoo]

The water pump fails to pump enough water to provide cooling water to the engine or push the PWC beyond idle speed. The engine output shaft to the impeller increases rpm at the PTO as the engine rpm increases but the water pump output does not increase (water dribbles out the tell tale). The impeller acts like it sheared a pin or key but none is shown on the parts list.

 

[JJinSC]

There is no pin to sheer. Only splines on the end of the shaft. Pull the pump, I think you will find it needs rebuilding.

 

[tobytd]

Certainly sounds like it may need a wearing

 

[gazzaskirepair]

Your impeller to shaft splines are history
Replace shaft and impeller and rebuild jet pump at same time

 

[jbunceseadoo]

I pulled the pump and surprise the shaft and impeller splines are both fine. The impeller clearance to the wear ring is in spec. I am waiting delivery of a impeller removal tool to disassemble the pump to troubleshoot further. There was only water in the jet pump oil supply but the impeller turns freely. I am sure the thrust and needle bearings will need replacement but does not explain why the pump isn't pumping water over idle speed.

 

[mikidymac]

Post some pictures please.

 

[jbunceseadoo]

Photos attached. The spline on the shaft and impeller are fine and the impeller has a tight fit on the shaft with the jet pump disassembled. New problem is the impeller shaft and bearings are shot. I didn't find the thrust bearing or thrust washer. So I am in for a pump rebuild. From the beginning I suspected the pump was starving for water or was ventilating air. When I removed the pump from the bulkhead mounts the upper bolts were not tight so I now suspect that air was being drawn in and ventilating the pump as the RPM increased eliminating the thrust. There was a lot of air in the jet. I can't prove this until the jet pump is rebuilt and properly reassembled which may not be this season. Thanks for suggestions.

 

[mikidymac]

Make sure you get a new rubber sealing ring for the pump where it connects to the hull.

 

[jbunceseadoo]

It appears to be part of the wear ring which I will replace. In any case I will augment with RTV gasket material and a proper torque and Loctite of the mounting hardware. Thanks

 

[mikidymac]

Is your ski the red Limited or gold RFI?

 

[jbunceseadoo]

The gold GTX RFI

 

[mikidymac]

On the RFI make sure you order a new neoprene seal. You should be using one even though they are not shown on the parts diagram for your ski.

 

[gazzaskirepair]

Did you remove the drive shaft and check the PTO splines ‍

 

[jbunceseadoo]

Great suggestion to use the neoprene seal. I did not pull the drive shaft but I did statically stress both ends of the drive shaft with cotton line in the cylinder head and there was no give. Also when I speed up the engine the shaft RPM immediately increases with no abnormal noise and little load on the engine. From the very beginning I suspected the jet pump was starved for water or trying to pump a lot of air. There was a lot of air in the jet stream, more than our older PWC. I am currently waiting for parts to rebuild the jet pump which will arrive this week.