98 Seadoo GS Suddenly Stopping

[Grizz]

I’ve got a 98 Seadoo GS that has ran completely fine since June. Now, suddenly, when riding with someone, it cuts out, sputters and seems to not have a lot of power. Remove the passenger and ride by yourself…it will sputter for 10-15 seconds and take off like a shot. Re-add the passenger and it goes back to sputtering and loosing power….any ideas?

 

[Lothsahn]

You sure it's sputtering and not cavitation? Cavitation would be high rpm but feels weird. Do you have an RPM gauge? Cavitation is pump is spinning but no go.

If you have a weak carbon seal your hole shots can be weird, and it gets worse with more weight.

 

[Grizz]

You sure it's sputtering and not cavitation? Cavitation would be high rpm but feels weird. Do you have an RPM gauge? Cavitation is pump is spinning but no go.

If you have a weak carbon seal your hole shots can be weird, and it gets worse with more weight.

Thanks for the reply, I really appreciate it!!!

Trying to explain this better as I don’t completely understand “cavitation.” and I am interpreting what my wife is explaining to me as I can’t ride it right now because I tore my ACL a month ago.

She said, when riding, at 3/4 to full throttle, the engine sounds like it’s under load and struggling to go with no power. Then, it all of a sudden took off like a shot and was normal again. She rode it around for 2-3 minutes then decided to circle around to get our son for the ride they had planned since it seemed normal again. Once he got on and they started to go, she said it immediately went back to the under load sound with no power again so she put it away and called me.

To answer your question, I don’t have an RPM gauge. She said “it feels like it’s under load and won’t go anywhere at 3/4 to full throttle.”

 

[Lothsahn]

Doesn't sound like how I would describe cavitation.

I had a similar issue on my 1996 GTX and it was a bad rectifier. The rectifier was confusing the mpem and making it misfire above 2500 rpm. You could try disconnecting the rectifier and see if the behavior changes. But I wouldn't expect it to rev high ever with that condition.

But there are so many things it could be. You're going to need to narrow it down.

Take a look at the intake and exhaust of the jet pump. Make sure there's no debris in there and that the wear ring is in good condition.

Have you replaced the fuel lines, or are they the original grey?
When is the last time you rebuilt the carbs?
Does your battery test good?
Have you verified the battery connections are tight?
When it's running poorly does pulling the choke out a little make it run better?

 

[Grizz]

Doesn't sound like how I would describe cavitation.

I had a similar issue on my 1996 GTX and it was a bad rectifier. The rectifier was confusing the mpem and making it misfire above 2500 rpm. You could try disconnecting the rectifier and see if the behavior changes. But I wouldn't expect it to rev high ever with that condition.

But there are so many things it could be. You're going to need to narrow it down.

Take a look at the intake and exhaust of the jet pump. Make sure there's no debris in there and that the wear ring is in good condition.

Have you replaced the fuel lines, or are they the original grey?
When is the last time you rebuilt the carbs?
Does your battery test good?
Have you verified the battery connections are tight?
When it's running poorly does pulling the choke out a little make it run better?

Thanks again, I REALLY appreciate the help!

To answer your questions….

1. No, they are still the original grey fuel lines

2. I’ve not tested the battery but it was bought new last year and on a battery maintainer all winter. I can have it tested though.

3. I asked to make sure the connections are tight…still waiting for an answer.

4. She said pulling the choke made it worse.

When leaving the dock at full throttle, it looks like it is at 1/4 throttle…then it suddenly kicks in and takes off like a rocket. There has also been a few times where it was going fine, she starts a turn then power dropped to 1/4 throttle despite still being at 3/4. The also sounds like there is a popping sound when the engine is running.

Fingers crossed, here is a video….the videos were full throttle the entire time.
Seadoo Engine Issue
Seadoo Engine Issue 2

 

[Lothsahn]

NOT cavitation. You can clearly hear the engine rev as the boat increases speed. The boat speed is directly related to engine rpm... So your pump is working.

I would disconnect the red rectifier wire to see if that resolves the issue. If it does, you need a new rectifier. That's an easy test and can cause these symptoms.

My guess is you probably have a fuel system (clogged hoses or fuel selector) or carb clogged issue. Given you're on original fuel lines, and probably haven't rebuilt the carbs, that's probably your issue. If you do a carb rebuild, make sure you use genuine Mikuni parts.

Regardless of this problem, if you're keeping the ski, you should replace all the fuel lines with grey automotive hose. The grey lines degrade inside and make a purple goo that clogs the carbs. If you starve the engine of fuel and it runs lean, you can destroy the engine.

 

[burtshaver2021]

See what everyone else thinks but sounds to me like it’s loading up with fuel, change out those grey fuel lines, clean the micro filters in the carbs and if that doesn’t fix it, rebuild the carbs with back to OEM kits from OSD marine.

 

[burtshaver2021]

NOT cavitation. You can clearly hear the engine rev as the boat increases speed. The boat speed is directly related to engine rpm... So your pump is working.

I would disconnect the red rectifier wire to see if that resolves the issue. If it does, you need a new rectifier. That's an easy test and can cause these symptoms.

My guess is you probably have a fuel system (clogged hoses or fuel selector) or carb clogged issue. Given you're on original fuel lines, and probably haven't rebuilt the carbs, that's probably your issue. If you do a carb rebuild, make sure you use genuine Mikuni parts.

Regardless of this problem, if you're keeping the ski, you should replace all the fuel lines with grey automotive hose. The grey lines degrade inside and make a purple goo that clogs the carbs. If you starve the engine of fuel and it runs lean, you can destroy the engine.

Agree, continuing to ride it like this could very well be damaging the engine, wouldn’t hurt to take a compression test

 

[Lothsahn]

Agree, continuing to ride it like this could very well be damaging the engine, wouldn’t hurt to take a compression test

+1 Definitely compression test before going through all the fuel lines and carb work.

Also sounds like loading up on fuel to me too. Thankfully that won't damage the engine.

 

[Grizz]

Thanks you both for taking the time to help me out!!!

How would I find the red rectifier wire? Is it in the black box on the side by the battery or in the grey box at the front of the ski?

As for a fuel issue, I wonder if this might be the problem as I have noticed a little bit of a fuel smell lately and there has been a slight appearance of 2 stroke smoke.

As for the carb, I has an issue about 8 years ago where the Seadoo would start and idle fine but as soon as you hit the gas it just choked out and died. I replaced the fuel filter but that did not solve the problem. At this point, since I did not know how to rebuild a carb for the micro filters, I just replaced the entire carb which fixed the issue. It’s been rock solid until now.

 

[burtshaver2021]

I suspect you may have multiple issues, possible leaking needle and seat causing it to load up below 1/4 throttle and possible blockages restricting fuel when it’s needed at higher rpm’s. Not sure about your machine, my 95 XP has the rectifier in the grey box

 

[Grizz]

I suspect you may have multiple issues, possible leaking needle and seat causing it to load up below 1/4 throttle and possible blockages restricting fuel when it’s needed at higher rpm’s. Not sure about your machine, my 95 XP has the rectifier in the grey

 

[Grizz]

Thanks, I’ll YouTube how to disconnect the rectifier wire to be sure. From what I understand though, it’s in the get box at the front. Once I split the box, the rectifier with the red wire is in the top left corner

 

[Lothsahn]

I have a 96 GTX not 98 GS, so it may be different.

On mine, the rectifier looks like this:
https://www.amazon.com/Regulator-Re...1921c46da1be30509c786dadd80aa0ff&gad_source=1

Bullet plug. Pulls out with a bit of force.

Recommend buying from OSDPARTS if bad. Amazon ones have been junk quality.

 

[Lothsahn]

Thanks you both for taking the time to help me out!!!

How would I find the red rectifier wire? Is it in the black box on the side by the battery or in the grey box at the front of the ski?

As for a fuel issue, I wonder if this might be the problem as I have noticed a little bit of a fuel smell lately and there has been a slight appearance of 2 stroke smoke.

As for the carb, I has an issue about 8 years ago where the Seadoo would start and idle fine but as soon as you hit the gas it just choked out and died. I replaced the fuel filter but that did not solve the problem. At this point, since I did not know how to rebuild a carb for the micro filters, I just replaced the entire carb which fixed the issue. It’s been rock solid until now.

If you're still running grey fuel lines it may have clogged your current carbs.

Minor smoke and slight fuel smell is normal on these 2 cycles at idle.

 

[Grizz]

OKAY….to “potentially” close the loop and for future people with issues….I was able to get out yesterday to take a look at it. Before delving into changing out the carbs, fuel lines etc. I decided to try to clean out the main fuel filter, replace the fuel filter screen and throw a new set of spark plugs in.

The filter cup had a layer of crud along the bottom. It wasn’t deep but the bottom of the cup was covered with what looked like very small rust coloured particles. As they were all loose, I used a nail and some paper towel to clean it out. The filter screen was yellowed and had several “rust coloured” spots all around it.

The plugs had a dry rusty colour on the ground electrode so, from what I understand, they are functioning normally and the machine is not running rich.

Once this was done, it appears to be running normally…with a little more power apparently. I have no idea when the fuel filter was replaced but the plugs were new last year. I might spend this winter replacing the entire fuel system just to be safe though. Thanks again for everyone’s help, I super appreciate it!!!