'97 GSX low revs?

[Vince Tilley]

I have a '97 GSX and have just serviced the carbs and adjusted as best I can without instruments. The manual says that the motor is rev limited at 7200rpm and I am getting around 6500rpm at full throttle. Is this normal given its age or should I be looking to get that 10% back?

By the way, was the seadoo designer a contortionist with several arms and small hands? What a difficult machine to work on when the motor is in the ski!

Thanks for any advice.

Vince

 

[seadoosnipe]

Rpm....

It's more likely your rpm gage isn't in calibration any longer. If the sound of your engine is good and it doesn't seem to be bogging down, I wouldn't worry with it. The tuning of your carbs doesn't require any special tools. Unless you re-jetted your carbs, I wouldn't worry with that supposed 10%.

 

[Dennis]

Rpm

Hi Vince,
I agree with SEADOOSNIPE. Odds are the tach is off. The tach should read about 6900 rpm. If the tach is correct and the engine is running smoothly then that would lead me to believe someone has installed the incorrect prop. Sometimes people install a aftermarket prop that is pitched to give the ski more top end speed. They get too aggressive with their selection of prop and the ski ends up going slower on top end (rpm's are lower) because the engine doesn't have enough horsepower to drive that prop. In other words the prop was designed for an engine that's been modified and has more horsepower than the stock engine.
DAWG

 

[seadoosnipe]

Ouch!.....

Ouch.....!.........o.k., you struck a nerve here. The word "prop" isn't applicable to the world of jet boats. I must admit it puts a thorn in my side when Seadoo enthusiasts use the word "prop", since the impellor has a completly different application! A prop (propellor) uses 3 or 4 blades on a shaft that is pitched to a certain degree to provide forward or reverse movement.
The impellor is a pump. It's a compressor type pump that spins in one direction, providing high pressure to a nozzle that in turn provides thrust. A reverse gate to change directions. The compressor has three sections. The low pressure side, the impellor chamber, and then into the high pressure nozzle. Forward motion applies more pressure to the low pressure side which in turn allows more pressure to be built in the high pressure side by the compressor.
Heres a little science test. When the craft is at WOT, look at the rear to see the amount of thrust being generated by the water blast. Then tie the craft up to dock and push the throttle wide open. You'll notice the water blast is significantly less. That's because there is no forward motion to build thrust.
O.K., I'll get off my soap box. But be fore warned. I own a Seadoo "Jet" boat. Not a Seadoo with an outboard motor and prop......:rant:

 

[kustomkarl]

I agree with you seadoosnipe! Prop??... Is this the wrong forum? lol Back to the problem...Check the throttle cable and make sure it is giving full throttle at the Wide Open Throttle(WOT). The boat should go from idle to WOT, when adjusted properly. Check it with the engine not running and give it a visual. It could be that it has slack on the full throttle position.
Karl

 

[Dennis]

Prop Vs Imp

That was the point I was trying to make. It sounds to me like someone installed a propeller in this jet ski instead of a impeller. I hate when people do that!
Dawg

 

[seadoosnipe]

Gotcha!

Ohhhhhh, I gotcha now. Sorry about that Dawg!.....I thought you'd been dipping into the sauce a little heavy for a moment there.....whewwwww, I'm glad you straightened me out on that one. :cheers:

 

[kustomkarl]

yea yea , that's what I ment.

That was the point I was trying to make. It sounds to me like someone installed a propeller in this jet ski instead of a impeller. I hate when people do that!
Dawg

That sounds like a good coverup Dawg...propeller, impeller...supeller, I guess they are all the same..lol:rofl::ack::cheers:

 

[Dennis]

Busted

Hi Guys,
Ok, I'm busted. My post about impellers vs propellers was meant to make fun of the hell I caught for using the wrong terminology. In my defense, at least I knew how to spell the it.(propellor?) LOL
Both of you guys are great and this dog needs people like you to keep him on his toes. Keep up the good work.
DAWG

 

[seadoosnipe]

All in fun my friend!

It's all in fun my friend. Look back in some of my post because I remember very well a time when I was looking for a solution to a problem with a RFI PWC and gave advice on checking the carbs.......!........yeah, I felt like the biggest dummy this side of the Mason Dixon line...but it happens to the best of us.
Karl, you want to add anything here, just jump right in. Or would you like me to make the statment for you.....:rofl:

 

[kustomkarl]

Uh...I plead insanity...I'm just crazy about this place. If we were all perfect none of us would be here. That's the fun of this forum, we can be corrected in a fun manor and move on. No harm done to anyone. We all get caught up in a topic, and sooner or later use the wrong terminology. I've done my share too Dawg, so don't feel singled out ...lol
P.S. we knew what you meant, I think
Karl