1997 GTX 787 only hitting 5k rpm

[Magic1973]

Hi guys, lookin for some pointers (already read every post on the internet including here and followed the advice but no fix yet)
Got a 97 gtx that stopped running right and was left in bits for a few years. Rebuilt it recently but cant get it beyond 5k on the water. Can rev the danglies off it on the trailer. Heres whats been done:
Crank seals, carb rebuild with oem, pop-off set and equal, fuel lines replaced, new coil, leads, plugs, mpem, rave valves (grooved upgrade)
Tested stator but got a ricks going in this weekend cos spark still looks weak to me, pickup tested and within spec, no movement or corrosion. Honestly i could assemble the damn thing from parts with one hand tied and my eyes poked out i been into it so much. But what am i missing?
Any help appreciated. Most posts seem to just end with no eureka moment. I assume someones advice worked for em but never posted which one once back on water

 

[JC-SUPERJET]

Possibly there is blockage or restriction somewhere in the Exhaust System. Rat's Nest, Mud Daubers or the Exhaust Hose has Cancer on the inside Walls. Check ALL Hoses and the Waterbox.

Have you tried adjusting the Carb High Speed Screws? Could be Lean. Try allowing more Fuel into the High Speed Circuit.

Do the RAVE Valves have brand new high quality Bellows? Old used ones can look okay but leak under pressure/high rpms/high load...Bellows loose their Elasticty with age.

 

[Magic1973]

Possibly there is blockage or restriction somewhere in the Exhaust System. Rat's Nest, Mud Daubers or the Exhaust Hose has Cancer on the inside Walls. Check ALL Hoses and the Waterbox.

Have you tried adjusting the Carb High Speed Screws? Could be Lean. Try allowing more Fuel into the High Speed Circuit.

Do the RAVE Valves have brand new high quality Bellows? Old used ones can look okay but leak under pressure/high rpms/high load...Bellows loose their Elasticty with age.

Carb high speed screws are shot -heads gone but haven’t moved em and has intermittently run at full for a few minutes leading me to an electrical problem. If stator don’t fix it i strip the exhaust again and check that. Its almost like hitting a rev limiter. Checked and replaced rectifier already and voltage is good at the batt when running. Bellows came with the used raves. But to be honest fitting em made no diff and I didn’t think old ones were bad either.

 

[etemplet]

There is a Seadoo Technical Service Bulletin concerning the 1997 GTX having problems in that RPM range.
Seadoo Service Bulletin 97-20. I had trouble with my wife's 97 GTX not transitioning past 5k and one of the members posted the bulletin. I followed it and Her ski flies now. I also spent a good bit of time with the carbs.

What is your pop-off setting? If that's not correct the ski will have problems. Are the needles holding tight. Generally my carbs hold tight around 30psi when I install a new needle, seat, and spring. Also if the ports in the barrel are not spraying good full streams you'll have trouble as well.

Good luck.

 

[Magic1973]

There is a Seadoo Technical Service Bulletin concerning the 1997 GTX having problems in that RPM range.
Seadoo Service Bulletin 97-20. I had trouble with my wife's 97 GTX not transitioning past 5k and one of the members posted the bulletin. I followed it and Her ski flies now. I also spent a good bit of time with the carbs.

What is your pop-off setting? If that's not correct the ski will have problems. Are the needles holding tight. Generally my carbs hold tight around 30psi when I install a new needle, seat, and spring. Also if the ports in the barrel are not spraying good full streams you'll have trouble as well.

Good luck.

Can’t remember the numbers now, I did popoff last summer but it was in spec and equal when i did it (had to buy a tester specifically in range) Also replaced the raves with good used ones per bulletin. Only thing that made any difference was new mpem as it was a slug to start as well as running like a sack of manure. Now starts on the button even after months with the battery off. I am where the ski is again next weds, will try the stator and update. It FEELS electrical but if its not that i look at the raves again. Also fitted a used rotary valve cover (i know all used stuff but otherwise so far the parts > the value of the 25y old ski. Clearances measured and in spec) old was grooved and massively worn. Checked rotary timing after -perfect.

 

[etemplet]

Just making sure... you installed the upgraded rave housings?
If it is carburation check that the ports in the throat are spraying good streams.
Also...verify that you have the correct impeller on the ski?

 

[Lothsahn]

Check the voltage of the sea doo with a multimeter as you rev it to 3-4k. It should not exceed 15V. If it does, it'll start misfiring. Should it exceed 15V, you have a failed rectifier.

Avoid revving too much out of water. The carbon ring doesn't get cooling, even though the engine does, and you don't want to damage it.

You can also test the rectifier by disconnecting the red wire (not the yellow wires) and driving the ski. Make sure you put electrical tape around the disconnected red wire so you don't short things.

Also make sure you have slotted rave valves. There's reduced clearance for the rave valves and they can start not opening correctly. There's a TSB about it (probably the one linked above). Clean the Rave valves or replace with the slotted versions if you haven't.

 

[Magic1973]

Check the voltage of the sea doo with a multimeter as you rev it to 3-4k. It should not exceed 15V. If it does, it'll start misfiring. Should it exceed 15V, you have a failed rectifier.

Avoid revving too much out of water. The carbon ring doesn't get cooling, even though the engine does, and you don't want to damage it.

You can also test the rectifier by disconnecting the red wire (not the yellow wires) and driving the ski. Make sure you put electrical tape around the disconnected red wire so you don't short things.

Also make sure you have slotted rave valves. There's reduced clearance for the rave valves and they can start not opening correctly. There's a TSB about it (probably the one linked above). Clean the Rave valves or replace with the slotted versions if you haven't.

Sadly already done all of the above, only thing I didn’t notice is whether the housings match the slotted valves. Will check that later today.

 

[Lothsahn]

If you're still stuck, try unplugging red wire from rectifier to see if it fixes things (be sure to surround with electrical tape to prevent shorting). If the red wire is unplugged, the rectifier can't be your problem (and isn't charging the battery).

You checked compression? Should be 150 on each cylinder. Below 130 it won't run right. Make sure NOT to use a harbor freight gauge--they're defective.

Revving out of water is easy. There's no load on the engine whatsoever. Low compression engines will rev out of water, but not even start in water.

 

[fatblockabody]

Raves, Water Regulator, Carbs, and blocked exhaust hose can all cause that issue if compression is good. I have personally had two separate exhaust hoses split internally and the inner liner blows up like a balloon and blocks off the exhaust when running, typically under load more so than on the trailer. Feel all around the exhaust hose for soft spots.

 

[etemplet]

Raves, Water Regulator, Carbs, and blocked exhaust hose can all cause that issue if compression is good. I have personally had two separate exhaust hoses split internally and the inner liner blows up like a balloon and blocks off the exhaust when running, typically under load more so than on the trailer. Feel all around the exhaust hose for soft spots.

As I like to say... these skis are sneaky bastards. LOL I got a RFI that won't cooperate at the moment.

 

[etemplet]

Sadly already done all of the above, only thing I didn’t notice is whether the housings match the slotted valves. Will check that later today.

It's not a match but there is a port inside the rave housing. The TSB tells you what to look for. Make sure when you install the raves that they don't drag on the gasket. They need to be completely free.

I'm leaning toward a carb issue on your ski but that and 50 cents won't buy you a coke. LOL Good luck and don't give up !!!

 

[AKnarrowback]

Replacing the rave housings is part of the TSB to correct the 5k hang up. Did you replace the housings?

If not, and you have the old housings, you can do a JB kwik job on the housing to build them up and see if that helps. I was skeptical on the TSB so I modified my housings as a test and the housing change was enough to get rid of the 5k problem. I slotted my valves and ordered the factory housings when I knew the update would work on my machine, the key point here is the housings solved the problem and not the slotted valves.

 

[POPPS]

Could be cdi/rev limiter?,,,are the butterflies fully open,

 

[DarrenR]

Hi guys, lookin for some pointers (already read every post on the internet including here and followed the advice but no fix yet)
Got a 97 gtx that stopped running right and was left in bits for a few years. Rebuilt it recently but cant get it beyond 5k on the water. Can rev the danglies off it on the trailer. Heres whats been done:
Crank seals, carb rebuild with oem, pop-off set and equal, fuel lines replaced, new coil, leads, plugs, mpem, rave valves (grooved upgrade)
Tested stator but got a ricks going in this weekend cos spark still looks weak to me, pickup tested and within spec, no movement or corrosion. Honestly i could assemble the damn thing from parts with one hand tied and my eyes poked out i been into it so much. But what am i missing?
Any help appreciated. Most posts seem to just end with no eureka moment. I assume someones advice worked for em but never posted which one once back on water

Sounds to me like the rave valves aren't opening. My 97 challenger (has 2 x 787 ) takes a little work to get rave valves to open but then quickly jumps from 5k to 7k rpm. Are you a big guy? My boat struggles more with a heavy load. Once it gets up to 5k I can pull back on the throttle the jam it forward and they usually kick in.
I've replaced bellows and etc and all appears OK. I need to rebuild the carbs with the correct mikuni parts. The guy who owned it before me had a mechanic to some shitty work. If you figure it out, let me know.

 

[Magic1973]

Ok sooo…. Rave valves replaced with newer slotted. But that wasn’t the problem: I gave up fettling all the peripheral stuff as none of it made a difference. Didn’t have a compression tester as mine had been the victim of something heavy and gravity. So i jus said sod-it and took the barrels off.


There was also a fair sized chunk of ring missing off the other barrels piston. Don’t know how it was even starting never mind hitting 5k. Getting it bored and rebuilding it. Barstool we bought from claimed he rebuilt it already but was years ago now
(tho only done mebbe 15 hours since). See what happens when i rebuild. Thanks to all who offered help. Will update with a final post after or beg more help if its still snafu.

 

[JC-SUPERJET]

Ya, Compression Test is the very first thing to do while replacing Spark Plugs on any "New-to-Me" PWC ...

You said "Rebuilt it recently", so naturally EVERYBODY assumed that the Top End was sound.

So now, you are REALLY going to rebuild it.

Sent us on a Wild Goose Chase...

 

[Magic1973]

what can i say, i am finishing a project for a dead friend i had a list of things that were already "done" so i started with all the things that weren't and didn't consider those things listed as fixed or ok.I fully intended to do a full rebuild anyway after i got everything else sorted - and the info i had was rebuilt 15 hours of running time ago. what it looks like is the previous owner did major damage and just threw a set of rings in knowing they would last long enough that no one would be bringing it back for a refund - comression tested on purchase was ok. but its been in bits since me mate died several years ago now and most of the info i had on it was word of mouth from him/prev owner.

 

[Magic1973]

Ok. Update. Top end rebuild done, compression is 155-160 if i trust my tester, ski starts on the button. Runs for a couple of minutes any rev range i want, then as soon as i let gas off and turn back to shore we back at 5k rpm (2 separate occasions same behaviour so I haven’t screwed something on first run ) at this point top end done, crank seals done, stator, mpem, coil, leads, new(updated) raves, carbs rebuilt. Checked fuel tank wasn’t pos/neg pressurised, plugs show pto side little wet, mag side as close to perfect as i have ever seen both low speeds at 1 turn. Highs not touched. Only thing i could find was crud in fuel filter (which was torn). Pulled carbs to check for anything that made it thru (will know tonight). Anything else that could make it run a dream for about 1-2 minutes every time out then just 5k?

 

[Magic1973]

Sorry, forgot all fuel lines replaced and fuel tap cleaned.

 

[Magic1973]

Finally got the ski running right, apart from some cavitation which i am gonna replace the wear ring and carbon seal for this weekend -final fix was new fuel filter and re-strip and clean carbs. Re balanced the throttles for both carbs as i noticed pto wasn’t opening as fully as mag side by a small amount <—- this was probably the rev limiting factor although all the other repairs made the ski easy to start and run well outside the WOT range and needed doing for the long term use of the ski. Thanks for all those that offered advice

 

[DarrenR]

Hi Magic, I believe the 787 not going past 5k is often the rave valve failing to open. Search a thread about how to check and rebuild. Sometimes it works to let off the throttle for a second then jam it back in to get it to open up