My patience is getting thin also. This thing is about to go on craigslist as a mechanic special. It would be a great ski if it ran right. Let me know if you speed sensor helps. My speedo works not sure how accurate it is, but it does work. Mine wont ever get to 7K tops out at around 6200.
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Cant reach max rpm's
- Thread starter Cornnutt
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update from this weekend. Someone told me it had to be in the RAVES so I tore them all apart again. Everything was clean, gaskets are good. The hole thats in the cylinder to make them work is clear. The guetine is marked top and is pointing at up at the plugs. Ran it without the seat and caps on they are moving up and down freely. When I ran it without the black caps it would only rev to 4K wouldn't ever go above even if the impeller came out of the water. Put the caps back on and ran the same as it always has 5K until the impeller comes out of water then 6200. Even when the impeller unloads and it runs at the higher RPMs its still about 500 shy of the rev limiter. It runs a little bit better with the red adjusters all the way in not much, but a little. Should I try some shims in there to make the spring harder to open?
How;s everyone else doing? Any luck yet?
How;s everyone else doing? Any luck yet?
russssellcrow
New Member
Went out yesterday in 97 Challenger/787. Tried feathering CHOKE, this worked a couple of times. Its weird...Das Boot could be running at 5000 RPM either before or after planing out, I pulled the choke and the engine dives, then push the CHOKE back in, and ZOOM! This baby topped out about 45mph at around 6800 RPM. It was interesting to note that it hit Rev Limit of 6800 with about 3/4 to 7/8 throttle (extra throttle had no effect).
Now I'm thinking there is a pressure problem in the carbs or fuel system. When the CHOKE is pulled, it instantly increases VACUUM to the CARB BODIES (ignore the engine RPMs diving for this analysis). Would the backside pressure cause the POP-OFFs to deliver LESS FUEL through the Hi-Speed Jets? I have the POP-OFF set to 30-32 psi currently (with 1.50 jets) . I'm thinking it needs a higher POP-OFF. Also, there is no flame arrestor screen (is this patently dangerous?) and the air cleaner is a big oval APE with a K&N oil treated screen filter. With this lower vacuum set-up, it seems the POP-OFF would need to be substantially higher, perhaps 38-42psi.
The other analysis would go something like this: The boat is running lean at HI-SPEED jets because of a fuel pumping problem (I have tried opening the HI jets up to 1/2 turn--no change) When it is idling, I can see tiny bubbles streaming quickly through the return lines, but I have not looked when it is running wide open because the back hood would get torn off by the wind. I guess I could confirm this by doing a high speed kill, then pulling the plugs to check their color, or by putting a fuel pressure gauge on the return line...
Now I'm thinking there is a pressure problem in the carbs or fuel system. When the CHOKE is pulled, it instantly increases VACUUM to the CARB BODIES (ignore the engine RPMs diving for this analysis). Would the backside pressure cause the POP-OFFs to deliver LESS FUEL through the Hi-Speed Jets? I have the POP-OFF set to 30-32 psi currently (with 1.50 jets) . I'm thinking it needs a higher POP-OFF. Also, there is no flame arrestor screen (is this patently dangerous?) and the air cleaner is a big oval APE with a K&N oil treated screen filter. With this lower vacuum set-up, it seems the POP-OFF would need to be substantially higher, perhaps 38-42psi.
The other analysis would go something like this: The boat is running lean at HI-SPEED jets because of a fuel pumping problem (I have tried opening the HI jets up to 1/2 turn--no change) When it is idling, I can see tiny bubbles streaming quickly through the return lines, but I have not looked when it is running wide open because the back hood would get torn off by the wind. I guess I could confirm this by doing a high speed kill, then pulling the plugs to check their color, or by putting a fuel pressure gauge on the return line...
I have a 97 seedoo speedster with the same exact problems. First start it you can run wide open till you run out of fuel but if you ever let out of the trottle it won't rev beyond 4000 rpm unless you hit a wake and get the impeller out of the water then it will take off again. My boat doesn't have rave valves. I have checked every forum on the net and this is a widespread problem that no one has the answer. Shop says just bring it in for a few weeks and let us rebuild everyting (according to them the new motors with 135 compression have to be bad) and when we are done then we will tell you how much it cost.
I don't think so either but you know mechanics, if you can't figure out the problem rebuild the engines.lol My instict tellls me it's a fuel delivery problem but I'm just not familiar enough with these boats to figure it out. The thing that baffles me the most is that both engines do the same exact thing at the same time. 2 different carborators, rectifiers, flame arrestors, ect shouldn't have the same problem at the same time. It's almost likes it's some kind of sensor limiting both engines.
russssellcrow
New Member
I GOT IT!!!
Opened the HI SPEED JETS 2 1/2 turns and this baby bolts out of the hole.
The big clue was when I would apply an instant of choke while stuck at 5000 RPM. The engine would drop and then roar. I knew the choke was causing high vacuum to form in the intake manifold, and that was forcing a mass of fuel out of the LOW and HIGH JETS.
So I finally took the advice of these board experts and did a CHOP TEST. You get the boat up to 7000 RPM, then pull the key, the engine dies. Then you take out a spark plug (they must be new) and check for fuel. Mine were dry as bone, so it was running very lean (lucky I put that Lucas synth race oil into the gas for break in).
Anyway, the air cleaner unit is an APE housing with a big oval K&N screen arrester. Makes the 787 run good, but tuning the carbs is no longer close to factory.
Here are final specs for baseline data:
1. new tigon fuel lines (see thru) , transparent inline fuel filter from Autozone.
2. compression 140 psi +/- 1 lbs each cylinder
3. NGK BR7ES gapped to 0.22 (one step hotter plug than BR8ES)
4. rebuilt carbs, set Pop Off to 32 psi +/- 1 lbs, 1.50 main jets, 0.70 idle jets
5. LOW JETS 2 turns, HI JETS 2.5 turns
6. APE velocity stack flame arrester with K&N Oval filter stainless and mesh filter
7. Pennzoil partial synth Marine 2 stroke oil thru injection system
8. cleaned fuel baffle, blasted out all lines with compressor
Good luck all!
Opened the HI SPEED JETS 2 1/2 turns and this baby bolts out of the hole.
The big clue was when I would apply an instant of choke while stuck at 5000 RPM. The engine would drop and then roar. I knew the choke was causing high vacuum to form in the intake manifold, and that was forcing a mass of fuel out of the LOW and HIGH JETS.
So I finally took the advice of these board experts and did a CHOP TEST. You get the boat up to 7000 RPM, then pull the key, the engine dies. Then you take out a spark plug (they must be new) and check for fuel. Mine were dry as bone, so it was running very lean (lucky I put that Lucas synth race oil into the gas for break in).
Anyway, the air cleaner unit is an APE housing with a big oval K&N screen arrester. Makes the 787 run good, but tuning the carbs is no longer close to factory.
Here are final specs for baseline data:
1. new tigon fuel lines (see thru) , transparent inline fuel filter from Autozone.
2. compression 140 psi +/- 1 lbs each cylinder
3. NGK BR7ES gapped to 0.22 (one step hotter plug than BR8ES)
4. rebuilt carbs, set Pop Off to 32 psi +/- 1 lbs, 1.50 main jets, 0.70 idle jets
5. LOW JETS 2 turns, HI JETS 2.5 turns
6. APE velocity stack flame arrester with K&N Oval filter stainless and mesh filter
7. Pennzoil partial synth Marine 2 stroke oil thru injection system
8. cleaned fuel baffle, blasted out all lines with compressor
Good luck all!
waterjunkie1976
New Member
Hey i got an issue goingon with my 96 GSX, just got it back from the shop after haveing the carbs cleaned(didntrealize how easy it was or would have done it myself) the PWC ran great plenty of torqueon the bottom end and topped out at about 55-60mph. after the first tank of fuel, the craft started running poorly, i lifted the seat off and seen where the inside was real damp to the point there was water on the plug wires.
The GSX also slowed dramatically in speed but the RPMs were extremely high(after drying the engine bay out) and the craft was in no way as responsive
any help or suggestions would be great!!!
Thanks
The GSX also slowed dramatically in speed but the RPMs were extremely high(after drying the engine bay out) and the craft was in no way as responsive
any help or suggestions would be great!!!
Thanks
I have a 96 Challenger that will not get up on a plane. full throttle limit in water is around 5K, (6.5 out of water). Just found that the Y connector on the fuel return line from carbs to fuel tank is broken off and open to the air on one side of the baffle where it goes into the tank (return from carbs). other side that goes into the tank (also return from carbs) is still connected, but has open side of y in line. could this cause the problem? Anyone care to explain the theory behind the fuel delivery system (hoses into and out of carbs)? (What is the purpose of the return from the carbs and the hose that goes from the block to the mag side carb?)
crisso
New Member
I just saw this thread.You said you got a new impellar.Was this the same time you did other work on the ski??
If this happened on a normal boat with an outboard etc.I would say the prop/impellar has a taller pitch.If you get it to spin,it will stay spinning untill you get it bogged down.If it was replaced,did you get back the same imp. with the same pitch?From what you posted,it sort of makes reason.
If it is the same pitch etc. horsepower is down and then you have to go back to the previous posts on this thread.
If this happened on a normal boat with an outboard etc.I would say the prop/impellar has a taller pitch.If you get it to spin,it will stay spinning untill you get it bogged down.If it was replaced,did you get back the same imp. with the same pitch?From what you posted,it sort of makes reason.
If it is the same pitch etc. horsepower is down and then you have to go back to the previous posts on this thread.
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