Why so slow?

[dperkinstx]

I have a '98 Sea Doo GTX RFI and a '99 GTX RFI. The person that sold me the '98 says it has larger pistons and should have better top end. What I really got was a ski that revs higher, goes almost 10mph slower (38mph max), is slower out of the hole, and uses almost twice as much gas. I don't even know where to start in figuring out why the '98 is such a dog. Any suggestions?

 

[Coastiejoe]

You have a cavitation issue. One of three places to look.
1). Something wrapped around the impeller or the drive shaft. But I doubt this is your issue as you didn't mention a vibration
2). Wear ring concern. The gap from the impeller to the ring should be NO MORE than the width if a dime.
3). Bad carbon seal / boot issue. It sucks air from inside the hull and puts air right where the impeller is.

Number 3 is a common issue. You can place two wire ties behind the bellows. This puts additional pressure against the carbon seal. If nothing else this is a great test to do. If it works you know what your winter project is. Replace the seal and all of it components.

Here is a link that contains a picture if the bellows.
http://www.seadooforum.com/showthread.php?66001-2000-Gtx-cavitation-New-owner-please-help.

 

[AdamXP800]

That 98 Gtx should be running mid 50s all day. Coastie has given you quality information

 

[dperkinstx]

I've worked plenty on old cars and 2-cycle motorcycles. I'm a newbie to PWC's, so forgive my ignorance.


Where are these bellows and carbon seal in which you speak? I have a service manual if you could point me to the correct picture.

The impeller & drive shaft have nothing wrapped around them. So it's not #1.

When I start the Doo on the trailer (flush hose connected), I hear a rattle. One of the Doo's rattles much more than the other. Is that a bad wear ring I'm hearing?

Could low compression be an issue? What should the compression be? I think they're something like 145 (front) and 110 (rear).

Neither of the Doos do mid 50's. The '98 tops out near 40mph. The '99 gets to maybe 47.

 

[AdamXP800]

If those compression numbers are accurate that engine isn't going to run well. I would double check the compression. Fuel off, plugs grounded, fresh battery, throttle wide open

 

[AdamXP800]

They should be pulling mid 50s all day.

 

[Sportster-2001-951C-Stock]

The gap between your wear ring and impeller should be no more than the thickness of about a dime, gravel, sand and swimmers being sucked through will tend to destroy the clearance.

http://fiche.seadoowarehouse.com/se...wc&a=254&vehicleid=1998-Sea-Doo-PWC-GTX---RFI

The Drive shaft has a carbon seal on it, which keeps air from being sucked through the drive shaft thru-hull into the pump and ventilating the impeller.

Here's the drawing. The rubber bellows item #9 acts as a spring and holds the carbon seal against the rotating SS sealing ring, Item #10:

http://fiche.seadoowarehouse.com/se...sp?Type=18&make=seadoopwc&a=254&b=17&Action=O

 

[dperkinstx]

Fuel off? There is no petcock on this model. Are you telling me to disconnect a fuel line or pinch it closed?

Plugs grounded? I remove a plug and screw in my compression gauge. Why would I need to ground the spark plug? I would think both plug wires should be disconnected so the Doo won't try to run on one cylinder.

 

[AdamXP800]

You have grounding post for the plug wires to go on. They are near the rear electrical box

 

[Sportster-2001-951C-Stock]

Fuel off? There is no petcock on this model. Are you telling me to disconnect a fuel line or pinch it closed?

Plugs grounded? I remove a plug and screw in my compression gauge. Why would I need to ground the spark plug? I would think both plug wires should be disconnected so the Doo won't try to run on one cylinder.

Ground the plug wires while the plugs are removed to avoid damaging the coil and electronics, this is standard procedure to disable an ignition system with no load.

Also, sparks from flying electrons can cause fuel vapors sitting in the bottom of a bilge to ignite, a real life safety hazard exists.

 

[summer]

If you do not have one download a service manual. Everything that has been listed here is explained in the manual along with some pictures. I'm not telling you to stop asking questions but the manual in combination with the advice given here is the best tools you can have for both this issue any anything else that comes along.

 

[Coastiejoe]

I've worked plenty on old cars and 2-cycle motorcycles. I'm a newbie to PWC's, so forgive my ignorance.


Where are these bellows and carbon seal in which you speak? I have a service manual if you could point me to the correct picture.

The impeller & drive shaft have nothing wrapped around them. So it's not #1.

When I start the Doo on the trailer (flush hose connected), I hear a rattle. One of the Doo's rattles much more than the other. Is that a bad wear ring I'm hearing?

Could low compression be an issue? What should the compression be? I think they're something like 145 (front) and 110 (rear).

Neither of the Doos do mid 50's. The '98 tops out near 40mph. The '99 gets to maybe 47.

Doo's rattle when running out of the water.

Click on the link I provided. There is a picture of the bellow. It is on the drive shaft.

 

[griz400]

the thickness of a dime is too much clearance -- a dime is .053 and .040 is the max, a new wear ring is like .005 and i like .015 or less -- thats my 2 cents

 

[dperkinstx]

I finally got my PWC out of the boat barn and brought it to the house. I will try the wire tie test this weekend. If the PWC runs better and I decide to replace parts, what all do I need to buy?

Ring Seal Carrier P/N 272000064
O-Ring (2) P/N 293300032
Ring Carbone P/N 272000770
Plug (Bumper) (2) P/N 272000019

Anything else?

 

[SabrToothSqrl]

STOP. before you buy anything, you need to address this sentence:

"What should the compression be? I think they're something like 145 (front) and 110 (rear)."

if this is accurate, your engine is shot, and nothing you will do will save it (besides a rebuild).

No impeller or carbs, or fuel lines, or pixie dust will do anything unless you have a working engine.

 

[dperkinstx]

STOP. before you buy anything, you need to address this sentence:

"What should the compression be? I think they're something like 145 (front) and 110 (rear)."

if this is accurate, your engine is shot, and nothing you will do will save it (besides a rebuild).

No impeller or carbs, or fuel lines, or pixie dust will do anything unless you have a working engine.

I bought this barge from a fly-by-night crook who's since been arrested & shut down. I was complaining to him about how slow this thing was, so he was doing some trouble shooting. I was looking over his shoulder and thought I saw 145 and 110 compressions. That was last summer.

I did my own compression test Tuesday night. The PWC was not warmed up at all. The compressions were 145 and 150.

 

[SabrToothSqrl]

That is within spec. continue

 

[Strizzo]

Before buying parts, a ride sans seat may tell you a lot. If you watch the carbon seal at idle, you will know if it is leaking. It will also let you watch for other oddities there may be hidden by the seat.

 

[dperkinstx]

I tried the wire tie test today...no improvement. I'll check the wear ring next. Any other suggestions?

 

[LouDoo]

I know I'm in this thread late and I have just skimmed over the thread and maybe this question has already been asked. What is the maximum rpm's you're turning, it should be in the neighborhood of 6800 to 7000 rpm. And at max. rpm what speed are you going? As far as you know are you running the stock impeller in your ski?

Lou

 

[dperkinstx]

I know I'm in this thread late and I have just skimmed over the thread and maybe this question has already been asked. What is the maximum rpm's you're turning, it should be in the neighborhood of 6800 to 7000 rpm. And at max. rpm what speed are you going? As far as you know are you running the stock impeller in your ski?

Lou

Yes, I'm spinning about 6800 rpm. I'm doing less than 40, maybe 38. As far as I know I have the stock impeller.

 

[FinnExplorer]

Where did you get your speed info from? From pwc's gauge or gps?

 

[dperkinstx]

Where did you get your speed info from? From pwc's gauge or gps?

I have two GTX RFi's. I'm running them side-by-side. My daughter (130 lbs) is on the slow one and I'm (230 lbs) on the other. I'm using the ski's speedo's for the speeds I'm stating, but the measurement that I'm most using is one ski walks away from the other. All the speeds I'm giving you are readings from my gauge.

 

[LouDoo]

Just making a WAG here, but everything being equal I think I would look closely at the carbon seal, check for misalignment, wear or if the surface is glazed. If the wear ring looks glazed, pull the bellows back and use a popsicle stick put a liberal amount of valve lapping compound between the wear ring a the stainless steel surface, it should take the glazing off the wear ring.

Lou

 

[dperkinstx]

Just making a WAG here, but everything being equal I think I would look closely at the carbon seal, check for misalignment, wear or if the surface is glazed. If the wear ring looks glazed, pull the bellows back and use a popsicle stick put a liberal amount of valve lapping compound between the wear ring a the stainless steel surface, it should take the glazing off the wear ring.

Lou

Read post #2 of this thread. I just tried the wire tie test. Wouldn't that have told me the carbon seal was bad?