Why is my GTX slower than my GTI?

[vtatt]

Hi everybody, and thanks for this forum.

New to jet skis, but kind of familiar with engines, big and small.

So we just got a 2008 SeaDoo GTI 130 SE, about 200 hrs. After a plug change and fresh gas it seems to be running great. Tops out at about 52 mph.

Decided that our family of four needed another (smh) so I got a 2003 SD GTX supercharged with about 140 hrs.

Took them both out in the water yesterday together and did some comparisons. My buddy is about 20 lbs heavier than me, and the GTI had half a tank. We did some “off the line” comparisons and the GTI seemed to always beat the supercharged GTX. GTX top end was maybe a little faster, but I’m still checking that out.

I was expecting the GTX to blow the GTI out of the water, no??? Is the GTX that much heavier that it won’t be much quicker?

Thoughts? No codes on either, and I think I hear a whistle of the SC.

 

[sktn77a]

Well, the GTX is an 18 year old boat so it's unlikely to be generating 185HP. It's also a lot heavier than the GTI but it should still be faster. However, I suspect the problem is with the wear ring. Check that out. Also, check the compression.

 

[vtatt]

Well, the GTX is an 18 year old boat so it's unlikely to be generating 185HP. It's also a lot heavier than the GTI but it should still be faster. However, I suspect the problem is with the wear ring. Check that out. Also, check the compression.

Thanks— wear ring “looked” ok, no damage. But next time I took it out I felt the obvious “skidding” feeing of cavitation, so that seems like the culprit. I don’t see any big dents/dings on the impeller, do people typically only change the wear ring? Or is a new impeller smart while I have everything taken off? Looks like wear ring is only about $45, but I’d want the kit with all the o-rings and seals as well, just to know I’m starting fresh.

 

[sktn77a]

What's the gap between the impeller blade tips and the wear ring right now? Are the blade tip worn down any? Usually, the impeller doesn't "wear" (unless you have a stainless wear ring), it just gets chewed up and looks awful!

 

[vtatt]

Plastic (white) ring. Impeller doesn’t looked chewed at all. I tried to look at the gap, but hard to tell way back there. My next invention is a long-reach gapping tool to sneak in there and measure (patent pending!!!!).

 

[POPPS]

To really see if the wear ring is worn, just pull the pump,..and send a pic of the prop.

 

[vtatt]

Here’s the best pic I could come up with before removing. Had to head to work, so more later.

 

[sktn77a]

Doesn't look too bad but the angle (parallax) could be hiding something.

 

[POPPS]

The 4tec should be much faster.,,is the supercharger working?

 

[vtatt]

The 4tec should be much faster.,,is the supercharger working?

That’s what I was expecting. I feel a little cavitation, so that’s why I’m looking at the wear ring. How would I test the SC? I hear a whistle similar to my turbo car, so I figure it’s at least moving.

 

[POPPS]

I don't think you should hear a whistle?,,,I check sc's by putting my hand around the hose that does from the outlet of the sc to the intake,,,then I rev the motor, the hose should swell.

 

[vtatt]

The whistle is subtle, so maybe my imagination. Can I try your swell check while on the hose? Or do you think it needs to be in the water? I want to try to spin the SC when I get home just to see if it spins freely. I don’t have a torque measuring wrench as a common video suggests, so I’ll see what I can do.

 

[POPPS]

No water needed for 30 or so seconds,,just start her up and give it a good rev, and I believe the sc should not spin freely.

 

[vtatt]

Haven’t checked the spinning yet, but the outlet hose certainly swelled a little when revved. So at least I can tell it’s doing something!

 

[vtatt]

so when I change the wear ring, I’m assuming I should also try to find the seal and o-ring kit as well? Seems like mostly what I find is single wear ring OR a kit for the whole impeller, ring, and seals.

 

[POPPS]

Not neccessary, you do not need to remove the cone to inspect all of the wear ring,,,just pull the pump,,and rotate the prop to see the entire surface if the ring,,,general rule,,is to hold the pump to the light,,,you should see less than 1 mm of space,,,wear rings usually maintain their space,,,it gouges that make deep holes,,,and cause cavitation,,
When you replace the pump, remove the venturi first, that will enable you to put a couple fingers in front of the pump to raise the drive shaft to align it with the prop,.then reattach the pump...
You do not need to replace the seals,,,if you need to remove the cone,,,and find some water,,,then usually its just the "O"ring on the cone.

 

[vtatt]

Doesn't look too bad but the angle (parallax) could be hiding something.

So I just measured with a long gap feeler gauge. It’s about .021, so not too bad. My GTI looks like .000000 comparitavely, but it’s a nearly new ring.

Some thin gouges on the GTX, not too deep in my opinion. I tried to angle the lighting to increase the shadows, but I think they’re pretty shallow.

 

[vtatt]

Also just noticed that the GTI has this boot that came loose somehow. I guess I have to re-lube the connection and screw it on. Wouldn’t think that should just “come loose” since it’s pretty new.

 

[POPPS]

If theres a thread on that boot,,,it is REVERSE...is there a rope up in the drive shaft cavity,,,does the gtx rev to spec?

 

[vtatt]

If theres a thread on that boot,,,it is REVERSE...is there a rope up in the drive shaft cavity,,,does the gtx rev to spec?

Thanks. Rev’ed up to the mid 7000’s, ran fine. No rope, just a little seaweed. Impeller/ring was changed right before I bought it, so I’m takin it to that shop today hoping they’ll just slap it back on. That connection is totally dry right now, so it needs synth grease and loctite.