1999 SeaDoo GTI Issue

[john15seadoo]

Hi all. I have an issue with my 1999 SeaDoo GTI and I haven't been able to find the solution online so I turned to this forum to see if anyone could help. The ski only goes about 20 mph at full throttle and at random points it will take off to about 45-50 mph, then after approximately 20-30 seconds, it'll drop back down to 20 mph. This past summer, the magneto was replaced, new battery was put in, carburetor was taken apart and cleaned and spark plugs were also replaced. Any help would be appreciated. Thanks!

 

[etemplet]

Just a few questions too help with troubleshooting.
What are you doing when it "all of a sudden" takes off? Are you hitting some waves thus taking some load off the impeller? So the RPM drops back down with steady input on the throttle correct? What does the engine sound like and have you tried easing the choke out at different points to gauge the engine's response? What does the spark plug electrodes look like? These engines and systems are sneaky...

Pulling out the choke a littl will help determine if the engine is rich or lean. What do you think the problem is?

 

[john15seadoo]

Hi thanks for replying so soon. When it takes off suddenly its honestly very unexpected, not hitting any waves or anything. It slows down on its own - it will do it even when holding the throttle at the same position. The engine sounds good and sounded even better after the carb clean but still had the same issue. I have not tried the choke. I also uploaded a picture of the spark plugs to this - they're new so they may not be the most accurate, however they're pretty white. I'm by no means a mechanic, but I believe they're not getting enough fuel. I'm thinking it could be the grey fuel lines that are notorious for going bad, they could be all clogged up. I ordered new fuel lines, they are arriving later this week. I'm just curious, could these fuel lines really cause an issue like that? It just seems very odd.

 

[mikidymac]

Plugs look a little lean but not bad.
Was your carb actually rebuilt using all new Mikuni parts or just taken apart, cleaned and put back together?
Also replace the fuel selector and fuel strainer o-ring when installing new hoses.

 

[Ckrawiec]

Based on your description of the ski, I'd suspect that the carb still needs to be serviced. Since the ski still has the grey tempo fuel lines, it is entirely possible that tiny bits of gunk have found their way into the carb passages and is impeding the free flow of fuel consistently through the carb and into the cylinder head.

So, replace all fuel lines, water separator O ring gasket, fuel selector valve and thoroughly clean the carb again (rebuild the carb preferably.... with gunuine MIKUNI carb parts)....then see how she performs after that.

 

[JeremyD615]

Yup! Replace the fuel lines, strainer o-ring and fuel selector (none of those parts are expensive), and then rebuild the carbs again with genuine Mikuni kits. The green goo from the grey lines doesn’t take long to funk up the carbs.

 

[john15seadoo]

Thanks for all of the feedback. Even though the grey fuel lines are still in, I decided to check compression this morning. Read 100 psi at both cylinders, which after reading online is 40-50 psi less than what it should be.

 

[john15seadoo]

Also the carb was fully taken a part and cleaned, it was not replaced with any parts.

 

[john15seadoo]

Just wondering if there were any other parts besides the ones in the picture I provided that I just replace when doing the fuel lines. Thanks!

 

[JeremyD615]

Buy an OEM selector rather than that JSP one. Some of those leak right out of the box, and OEM is not too much more. Also, try a different compression gauge. If both cylinders are fairly even at 100psi, I’d suspect the gauge before the engine...

 

[mikidymac]

And no Harbor Freight compression gauges.
You need to replace the parts in the carb with new Mikuni, not just taking it apart.

 

[john15seadoo]

Okay I’ll try out a different one. And of course lol, the one I picked up was from Harbor Freight thinking I’d only use it once. Also could the wear ring have any impact on this issue? I was told to check that out as well.

 

[JeremyD615]

The wear ring can cause cavitation, but this sounds like a fuel problem. When you have excessive clearance at the wear ring, it will feel like a clutch slipping and the engine will rev to the moon without the ski really going anywhere...

 

[mikidymac]

Okay I’ll try out a different one. And of course lol, the one I picked up was from Harbor Freight thinking I’d only use it once. Also could the wear ring have any impact on this issue? I was told to check that out as well.

LOL, you are about the 5th person this season that has already been bitten here by the Harbor Freight compression gauge.

 

[JeremyD615]

Yeah, just for reference, a harbor freight gauge showed about 105psi on both cylinders of one of my good engines, and a Snap-On gauge showed 146-147. They aren’t reliable at all...

 

[john15seadoo]

Thats funny lol. I’ll pick up a new gauge and test it out. I removed all of the fuel lines today and labeled them for easy installation. Just have to wait for the fuel selector to come in. I posted a picture of the fuel lines - green / blue sludge as expected.
I also took out the fuel tank baffle since my fuel gauge is not working. Everything was intact, however the circuit board seems to be slightly wobbly at the bottom. Any ideas on what to look for with this issue as well? Sorry for all of the questions, just trying to fix everything at once while its all out. Thanks.

 

[mikidymac]

The circuit board does move around a little and especially if the bottom cover is missing.

Put a multimeter set to ohms ont eh fuel sender wires. They should go up and down with the float. If there is no continuity it's the F1 fuse that can be bridged.

 

[POPPS]

Just a few questions too help with troubleshooting.
What are you doing when it "all of a sudden" takes off? Are you hitting some waves thus taking some load off the impeller? So the RPM drops back down with steady input on the throttle correct? What does the engine sound like and have you tried easing the choke out at different points to gauge the engine's response? What does the spark plug electrodes look like? These engines and systems are sneaky...

Pulling out the choke a littl will help determine if the engine is rich or lean. What do you think the problem is?

 

[POPPS]

Great idea on the choke pull E

 

[POPPS]

Hi thanks for replying so soon. When it takes off suddenly its honestly very unexpected, not hitting any waves or anything. It slows down on its own - it will do it even when holding the throttle at the same position. The engine sounds good and sounded even better after the carb clean but still had the same issue. I have not tried the choke. I also uploaded a picture of the spark plugs to this - they're new so they may not be the most accurate, however they're pretty white. I'm by no means a mechanic, but I believe they're not getting enough fuel. I'm thinking it could be the grey fuel lines that are notorious for going bad, they could be all clogged up. I ordered new fuel lines, they are arriving later this week. I'm just curious, could these fuel lines really cause an issue like that? It just seems very odd.

 

[POPPS]

Yup, the guys will agree, those grey lines will become a fuel starvation gremlins.

 

[john15seadoo]

I’m just waiting for the new fuel selector to come in, should be coming in tomorrow. Then I can put the new fuel lines in and see. I also picked up a new compression gauge, its made by Actron. I checked the fuel baffle, there is no continuity when moving the magnet up and down the column across the circuit board, so the f1 fuse has to be bridged or the baffle replaced. Will provide an update on compression once the fuel lines are back in. Just a quick question - how would I use the choke to determine how its running? Thanks.

 

[POPPS]

Sometimes, choking the motor as you ride, and it partially cures the problem, helps you identify a fuel starvation problem, and to rule out other possible issues.

 

[john15seadoo]

Changed the fuel lines today, new fuel selector in as well. Just wondering how to prime the fuel lines? Does the bottom fuel line at the carb have to come off and suck fuel through it, then reconnect? Also tested compression on the new gauge. 125-130 psi at the front, 135-140 psi at the back.

 

[mikidymac]

Compression is low and there shouldn't be 10 psi difference between them. I would get a second gauge.

To prime remove the return line from the carb then cap it with your thumb. Then blow air into the tank vent to put some pressure in the tank and as soon as fuel starts to flow out of the return carb fitting put the return hose back on and the lines and carbs are primed.