The "seadoo knock"?

[Jeffspx]

Ive been breaking in the rebuilt motor i put in my 94 spi. Bought the ski blown up cheap. Almost thru the first tank.
While idling in the water, i hear a knocking noise, almost sounds like somethings banging on the inside of the hull. It stops immediately I throttle off idle. I dont think its in the motor or anything. I rode around with the seat off briefly and couldnt hear it with the seat off. I dont hear it on the trailer. I do hear normal pump rattle though when on the hose, I am familiar with that.
I do NOT have an anti rattle pump cone, I will be getting one. I checked motor mounts and check every time the seat is off too, i checked to make sure the exhaust isnt hitting the hull. The drive shaft splines looked good felt tight on each side when installing the motor, and I did align the motor when installing. I searched and people mention the seadoo rattle. Does this sound like it? It sounds like something knocking on the hull.
Thank you all for any help.

 

[Dr Honda]

Don't waste your $$$ on the anti rattle cone. I've seen them melt and cause more problems that they solve. The knock doesn't cause problems... and as you know... it's normal. Just grease the shaft, and make sure the bumpers are in both ends.

 

[mwat65]

As Dr H says if the knock is really noticeable it’s the driveshaft bumpers. You wouldn’t believe how many skis I’ve seen without the bumpers. More than I’ve seen with them.

 

[Jeffspx]

Thank you guys. Its good to know that its most likely not an issue. Driveshaft was installed with new bumpers and greased with waterproof grease.

 

[Dr Honda]

The bumpers help a lot. The knock is from the pump itself. If built correctly... there is a rather large allowance in the lateral movement in the pump shaft. Since it's on roller bearings, and has a large seal surface... the impeller and shaft can simply move forward and back in the bearings. AND... since the fiberglass hull is a big acoustical box... the knock gets amplified. Yes... it sounds bad... but it's very normal. Once you bring up the throttle... the pump loads, and should stop making noise. If it's still knocking while at speed... then somthing is wrong.

 

[GGuillot]

Don't waste your $$$ on the anti rattle cone. I've seen them melt and cause more problems that they solve. The knock doesn't cause problems... and as you know... it's normal. Just grease the shaft, and make sure the bumpers are in both ends.

Really? Melt? Seems improbable, the anti rattle cone keeps a slight pressure against the shaft, and sits in synthetic oil. I'm redoing a GTX and a GSX and they both look fine.

 

[mwat65]

I’ve seen it twice with the anti rattle cone. They were melted and smashed to hell and gone.

 

[Chester]

Turn your idle up and the knock will go away. It's idling too slow. The only time I've seen a melted anti-rattle cone is when water got in and the oil leaked out. Otherwise, they work well.

Chester

 

[Jeffspx]

Turn your idle up and the knock will go away. It's idling too slow. The only time I've seen a melted anti-rattle cone is when water got in and the oil leaked out. Otherwise, they work well.

Chester

Thanks for all the advise guys. I had considered whether my idle was too low anyhow. I will turn it up just a tad.

 

[Dr Honda]

Really? Melt? Seems improbable, the anti rattle cone keeps a slight pressure against the shaft, and sits in synthetic oil. I'm redoing a GTX and a GSX and they both look fine.

Yep. When my shop was open... I would see at least one a year. (and dozens posted here over the years) Some are made from better materials that others. If the plunger was made from a Teflon rod... they would be fine. But most are just made from UHPE. If the oil is low... they melt. Not to mention... the new cone, plunger, and spring are now occupying the space where the oil should be, and the cone now holds les oil.

But regardless of that... the knock is just a noise, and it's not causing any issues. So... the pushers are just wasted money.