Knocking noise in hull of a '98 GTX,only when in water.

[herb165]

I just had a motor installed but the noise was their prior to that,you can only here when in the water and sounds like in the pump area,pulled the pump and took it to the dealer and he said the bearings were fine and ask me what the idle was set at,1350 i told him and he said to low and i adjusted the idle to 1500 in the water and the noise stops but when you shut down just befor it stalls you can here the knock still faint but still there,i need help please,it was loud enough when the idle was low if you were idling together thru a no wake zone you could here it

 

[Seadoobuddy]

This is pretty much normal sound at low engine speed. As there is not a big load on the impeller.
I bet it's a lot worse if you start it on the trailer.
It goes away at higher speeds doesn't it?

 

[seadoodoopartsofcf]

They sell a spring set up you can install in the cone to eliminate that sound...the shaft in the jet pump is a full floater that bounces back and forth. Also you may what to check the rubber stops on the ends of your driveshaft to see if they are still there.

 

[herb165]

yes on the trailer it is louder,but i turned the idle up today to 1500 and it seems to be gone until the very last second befor shut down,i thought i was doomed and was headed to the dealer in the morning,but thanks alot.

 

[herb165]

replace the rubber stop and the impeller felt spring loaded when i pushed on it when i had it out of the ski,the new anti ratlle nose cone ,will that fit the 98 as well

 

[Seadoobuddy]

Actually through other users of the anti-rattle cone, I've heard the noise soon comes back as the cone spring wears out.