Cavitation and top end power loss

[RKH]

Hey All,

I am new to the forum, and this is the first one I have owned. My 09' RXTX 255 has new pump, wear ring, and impeller, new plugs, throttle is tight. I am having cavitation at 4200rpms, and have lost top end power (55 mph top speed). Thanks in advance.

Rog

 

[skiasylum]

Did it ever run correctly after all the new parts were installed?

 

[RKH]

The engine was rebuilt and new SC kit installed. Excellent excelleration, but somewhere around 4200 rpms, it cavitates and shutters under my seat, and then it seems fine at planing and is smooth around 5000 rpms and up. Last year I had 8200 rpms and a top speed of 64mph. This year its more like 7200 rpms @ 54-55 MPH. 91 octane.

 

[Digdog]

Sounds like the wrong impeller was installed or you sucked up some debris and it's stuck in the impeller. Sometimes an aftermarket impeller on a stock engine will drastically drop the rpm's , find out which impeller was installed so you can see what pitch it has.

 

[RKH]

Sounds like the wrong impeller was installed or you sucked up some debris and it's stuck in the impeller. Sometimes an aftermarket impeller on a stock engine will drastically drop the rpm's , find out which impeller was installed so you can see what pitch it has.

 

[RKH]

The parts are stock from a BRP dealer. I am not sure of the impeller pitch, but it was ordered for the rxtx 255. There is no debris sucked in the intake grill ie. Weeds or sand or sticks, or muskrats. I am wondering if the shaft is out of balance or I had read about a carbon ring? Could this be a potential problem?
I appreciate the help.

 

[skiasylum]

Were still not quite sure if the ski ever ran right after all the work was done it? Did the dealer do the install? Yes, bad carbon seal can cause cavitation. Was the engine and pump properly aligned during install?

 

[MacSeaDoo]

Are you getting any water in the bilge?

 

[RKH]

Hi All, sorry for the delay, just getting back from vacay. No there is no water in the bilge, so probably not a carbon ring. The engine and pump were aligned with a tool during the install. I think I need to go back to the supercharger or fuel system??

 

[MacSeaDoo]

I would check all of you intake hoses and clamps first to make sure they are all seated and tight. That includes on the Intercooler(IC). If you are mechanically inclined, you could pull the IC and pressure test it. The other method is to pull the hose from the IC to the Throttle body at the TB and run the ski on the hose for a bit to see if water starts trickling down that hose.

Like others mentioned, if the parts are right you should be good to go.

 

[RKH]

I would check all of you intake hoses and clamps first to make sure they are all seated and tight. That includes on the Intercooler(IC). If you are mechanically inclined, you could pull the IC and pressure test it. The other method is to pull the hose from the IC to the Throttle body at the TB and run the ski on the hose for a bit to see if water starts trickling down that hose.

Like others mentioned, if the parts are right you should be good to go.

Okay thanks! We did peessure testing on the intercooler 4-8 weeks ago, no leaks. I will recheck all the hoses. Maybe even pull the supercharger and check torque.


R.