04 GTX Supercharged not at max rpm's

[dtowe034]

Hello,
Im new to forums so please be patient with me. I have a 2004 GTX Supercharged seadoo. I bought it 3 weeks ago and i noticed that i was getting low thrust but good high-end speed 60-62mph. I checked the wear ring and the impeller, and both were damaged. I was getting about 7200 rpm's with the damaged parts. I replaced both the wear ring and the impeller with a Solos 12/20. It now does great on both low and high-end, but the rpm's are at 7000 - 7050 at top end. I saw in the shop manual that this unit has a max rpm of 7500 +-50. First of all is that true that the rpm's should be a 7500 at full throttle? If so where should i be looking for the loss rpm's.

Thank you for any help.

 

[Dr Honda]

Welcome.


It looks like your rev-limiter is set at 7650 rpms, and yes... your peak HP should be at 7500 rpm.

The first thing I would check is that all your intake pipes are tight. If you are loosing boost, you will loose RPM's. Also... make sure your supercharger isn't slipping. Reach in, and give the impeller a twist. If you can move it... it needs a rebuild. Speaking of that... when was it rebuilt last?

If that all checks out... check your compression, and your valve clearance. If your compression is low, or if your valves are tight, you will start to loose performance.

 

[dtowe034]

Thank you for the quick response. I will check all of the items on the list, and i dont know where or if ever the supercharger has been rebuilt!!!! There is only 86 hours on the unit, but im not sure if that has anything to do with it.

 

[dtowe034]

I checked the supercharger and it is tight. How do i check valve clearance? I did replace the spark plugs and got the rpm's to 7300, but on average it stayed at about 7250. Thats some improvement , but not 7500. Is it possible that this engine is what it is. If it was not broke in right, could it cause it to have lower rpm's then average?

 

[dtowe034]

Sorry i forgot the intake is also sound.

 

[Dr Honda]

at 7300... that's almost what I would call acceptable. Normally, seadoo's are designed to run just a few hundred RPM under the rev limiter.

One thing that comes to mind is the last owner could have changed the impeller, and it's just loading the engine a little more than the factory impeller did. (that would cause a loss in RPM) Also, if there is a deep, top loader intake grate... that will drop top RPM's.

Regardless... since that ski is as old as it is... I would have the supercharger rebuilt. If the washers break... it will kill the engine. (an engine rebuild will cost more than the ski is worth)

To check the valve clearances... you need to take the rocker cover off the engine, but to check compression... you just take out the plugs, and thread in the gauge.