99 GTX Limited sluggish acceleration

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andy.262

andy.262

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After reading countless posts on possible issues, I finally decided to create an account and post my exact issue to hopefully avoid doing unnecessary work.

So I just bought my 2 skis (99 GTX LTD and 97 SPX). The SPX takes off like a rocket (well, not compared to a newer ski but for '97 not bad) but the GTX feels slow and sluggish. It was my understanding that these should be a similar speed, but the GTX accelerates much slower. So - what should be the very first things I should look for to try and find the source of the problem? I'm not afraid of doing some homework and taking things apart, but if I don't need to I'd rather not. Although I admire people who work on engines often, I unfortunately don't have much experience.

I've seen people point to carbs RAVE valves pretty often. RAVE valves seem easy enough to take apart and clean, I'll probably take a swing at that tonight. Anything else that I should look at before trying to learn how to remove/clean the carbs?
 
If your top speed is close or just over 50 and out of the hole acceleration is sluggish for the first 10/15mph, then I would say it's running right. These are slow planing so at first they are a little slower
 
Alrighty then I guess the problem is that there is no problem! Or at least, I think there's no problem. The speedometer doesn't work but I feel like I can probably get going to about 50.

Any way to adjust the trim on these? I feel like I could benefit from having the nose pop up a little more.
 
Short answer on the trim - no.
Long answer - with enough parts, maybe. It has reverse so it's more complex.

1. check compression - within 10% of each other - ideally 120-130. If one is 70, the other 100, you're shot. If both are 100, you could be fine.
2. check fuel lines - search forum for grey tempo lines - they have to go.
3. using correct oil?
4. PERFECT condition/world you should see 7,000 RPM WOT on the water. (6700-6800 is fine for most ppl).
5. take off with a 951 should be brisk, it should shoot up to about 4-5k then slowly raise to 7k WOT
6. 99GTX951 (I owned 3) should be 55MPH top end, possibly 60 on the widely inaccurate paddle wheel.


Other stuff:
Fuel Filter, oil filter
Water box / Regulator
Spark Plugs - correct ones!
Trim back plug wires trick
Clean RAVES / inspect.

I think the 99 didn't have TPS, but I could be wrong. Maybe that was added in 2001.


etc etc. :)
 
Hadn't even thought about the reverse adding to trim complexity, guess that explains why they didn't add it in the first place. Both skis still have the grey fuel lines. Guess I'll be learning how to do that job soon! Unfortunately both the digital and analog speedometer are broken on it so I really can't tell what speed I'm getting to.

I'll test the compression next week sometime - going away this weekend. If they are not within 10% of each other, what does "shot" mean? Is that "shot" as in the whole engine is shot, or as in I need to get a few more parts to replace?

Also found out that the previous owner had been using Penzoil Marine 2-stroke oil, not SeaDoo oil :(. Discussions on whether that's OK or not seem to be inconclusive at best. I've read somewhere that changing oil types can cause a reaction or something and hurt the engine unless the old oil is all drained first. Will I have to do that in order to switch to the SeaDoo oil? Tuesday was my first time taking them out and the previous owner had topped them off with oil before giving them to me, so I haven't had to add any yet.
 
andy.262 said:
Hadn't even thought about the reverse adding to trim complexity, guess that explains why they didn't add it in the first place. Both skis still have the grey fuel lines. Guess I'll be learning how to do that job soon! Unfortunately both the digital and analog speedometer are broken on it so I really can't tell what speed I'm getting to.

I'll test the compression next week sometime - going away this weekend. If they are not within 10% of each other, what does "shot" mean? Is that "shot" as in the whole engine is shot, or as in I need to get a few more parts to replace?

Also found out that the previous owner had been using Penzoil Marine 2-stroke oil, not SeaDoo oil :(. Discussions on whether that's OK or not seem to be inconclusive at best. I've read somewhere that changing oil types can cause a reaction or something and hurt the engine unless the old oil is all drained first. Will I have to do that in order to switch to the SeaDoo oil? Tuesday was my first time taking them out and the previous owner had topped them off with oil before giving them to me, so I haven't had to add any yet.
Click to expand...

Nothing inconclusive about it at all, that is the wrong oil for the Seadoo and will cause issues from crank seal leaks, stuck RAVE valves and on 951's seized pistons.

By engine being shot that means new top end but on a 951 a higher hour crank will not survive a new top end so in your case, yes, replace the crank, rebuild the balancer and pistons, rings and bore cylinder.
 
I'm a reasonably determined DIY-er but most of my experience is in electronics and computers, not engines. Is this a job that I could pull off myself after doing some research or is it something I should have a professional do?

As of now it starts right up and doesn't stall, moves through the water pretty well just a little slower than it probably should be. Am I good for a few more rides to finish out the season (probably only time for 2 or 3 more rides, upstate NY weather :confused:) or should I be doing this stuff immediately?
 
IF it were mine I would do it immediately as I have seen engines seize for lack of maintenance the first time out.

Complete fuel system service with the correct parts. Drain and flush oil system with correct seadoo oil and filter. Clean RAVE valves.
 
andy.262 said:
Hadn't even thought about the reverse adding to trim complexity, guess that explains why they didn't add it in the first place. Both skis still have the grey fuel lines. Guess I'll be learning how to do that job soon! Unfortunately both the digital and analog speedometer are broken on it so I really can't tell what speed I'm getting to.

I'll test the compression next week sometime - going away this weekend. If they are not within 10% of each other, what does "shot" mean? Is that "shot" as in the whole engine is shot, or as in I need to get a few more parts to replace?

Also found out that the previous owner had been using Penzoil Marine 2-stroke oil, not SeaDoo oil :(. Discussions on whether that's OK or not seem to be inconclusive at best. I've read somewhere that changing oil types can cause a reaction or something and hurt the engine unless the old oil is all drained first. Will I have to do that in order to switch to the SeaDoo oil? Tuesday was my first time taking them out and the previous owner had topped them off with oil before giving them to me, so I haven't had to add any yet.
Click to expand...

Heed the advice above, address things now, both skis have the grey (tempo) lines like you say I wouldn't ride them further at all. There's numerous stories on here of people going out a few times and putting this off, then they regret it. The old grey lines do not hold up well to the enthenol fuel today, they gum up and make it's way into the carbs causing issues or worse a lean issue. A simple $25 fix turns into hundreds quick. Personally, I'd go a step further and remove the carbs and go through them.

The analog and digital speed gauges are tied together, you likely have the paddle wheel on the ride plate sticking or something.

I'd drain the oil, flush, clean, and fill with the proper oil now, no going out any more. Seadoo XPS synthetic is a good oil, recommended for RAVE valve 787 and 951 engines.

If these are newly acquired skis, one area I'd look over is jet pump maintenance, I'd check that out, flush and fill with fresh oil at a minimum.
 
Got out all the Penzoil the previous owner was using and re-filled with XPS full synthetic. Looks extremely similar to the stuff my dad uses in his Ski-Doo sled.

Going to do new fuel lines this week. Can I just use any appropriately sized fuel lines from an auto parts store, or do I need to get "marine grade" lines or something like that?

Also, I know there are fuel lines coming off of the fuel tank and I know there is 1 (or 2?) between the carbs on the 951, are there any others anywhere that I need to replace?
 
Standard automotive fuel hose is what I use. Yours take 5/16 for everything but the return line which is 1/4”.
 
mikidymac said:
Standard automotive fuel hose is what I use. Yours take 5/16 for everything but the return line which is 1/4”.
Click to expand...
Awesome! thanks to everyone responding on this thread, this is all new to me and you guys are really helpful.

I think I remember reading somewhere I'd need about 25-30 ft of line, does that sound correct? Also, does my other ski (97 SPX) use the same size/amount of line?
 
andy.262 said:
Awesome! thanks to everyone responding on this thread, this is all new to me and you guys are really helpful.

I think I remember reading somewhere I'd need about 25-30 ft of line, does that sound correct? Also, does my other ski (97 SPX) use the same size/amount of line?
Click to expand...

Your 97' SPX uses only 1/4" everywhere for fuel. Figure 20'-25' per ski for the amount fuel line you'll need.
 
It depends on the model of ski but I can usually do close to two on 25' of hose. For both your skis you should be fine with 25' of each size. You don't need to change the fuel tank vent hose or the small accelerator pump hose. Now would be the perfect time to change the small 3/32" oil injection lines too.
 
If you change the line on the accelerator pump on the PTO-side carb, be careful there is a small jet inside that line.
 
GregM64 said:
If you change the line on the accelerator pump on the PTO-side carb, be careful there is a small jet inside that line.
Click to expand...

Greg is correct and there is no reason to change those lines unless they are physically damaged as they don't go bad.
 
Lines changed out!

Didn't find a ton of green goo in there but there was definitely some. The 951 engine was a big pain to work around compared to the 787. I've got new fuel filters on the way for both.

I wasn't able to change out the 2(?) short lines that go between the carbs on the 951 (removing the carbs seems like an ENORMOUS pain). How risky is it to just leave those there now that all the other lines are new?

As a note for anyone reading this in the future - I used about 17ft of 5/16 line on the 99 GTX, and about 20ft of 1/4 line plus about 5ft of 5/16 line on the 97 SPX. This was with cutting the new hose to pretty much the exact length of the old hose. Also, the 97 SPX had about 6-8 crimped hose clamps that cannot be re-used. I found the easiest way to remove them was to just take a pair of *sharp* cutters and cut them right across the top of the crimped hump (very technical terms, I know) parallel with the hose and then they got loose enough to pull the hose off. I had to go buy a bunch of normal gear clamps like these to replace them when I put the new hose on. Not a big deal as they less than $1 per clamp.
 
ALSO, I did compression tests on both skis yesterday and got about 110 on each cylinder for the GTX, and about 135 on each for the SPX. I think thats a bit low for the GTX but at least they came out the same. Going back to the original purpose of this thread, would low-ish compression contribute to slower acceleration for the GTX?
 
Think I found the source of my acceleration issue - am I crazy or do I not even have a wear ring anymore......


no wear ring.jpg
 
Just ordered a Derlin ring from SBT last night!

In order to do this job myself I will also need an impeller tool and a new neoprene seal ring, correct?
 
Holy **** guys, it feels like a whole different machine! Takes off quickly and revs higher than I've ever seen it go before. It even sounds, well, healthier I guess!

Thanks so much for the help on here, I'm not sure I would have been able to get this far without it
 
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