Super Jet Limp Mode?

[naticen]

I've got a 650 square that just started having an issue last week. It will run perfectly fine for sometimes 5 minutes or sometimes not at all and then out of nowhere, it feels like it hits hits limp mode and won't even plane. I describe it like that because it's either on or off. It'll always fires up instantly and runs perfect except the idle is a little hit and miss if this so called limp mode is on. I've never had had it kick in limp mode and I have definitely over heated this ski a few times so I don't quite know what limp mode is. It did feel hot and we did drag it through sand to get to the water and then ride some low trails. I flushed it all out and got the engine very cooled down and then it hit limp mode real quick when I put it back in, so I don't think it is actually overheating although I don't know if a faulty temp sensor would cause this. I pulled plugs and the rear one looked good, except wet with fuel like it wasn't firing. The front looked perfect. Any ideas on where to start?

 

[escore]

Could be a bad sensor. Most people unplug the over heat. If I remember correctly its the pink wire in the E box. If its running on one cylinder like you described with the plugs it could be that too.

 

[CRJ]

id consider a case leak, over heat sensor or a bad sparkplug. try the plugs first, then unplug the sensor (pink wire) and then try a leak down test if all else fails.

 

[JetManiac]

Unplug pink wire in ebox to bypass temp sensor but be careful and make sure you are not actually overheating.
Also check fuel tank vent.

 

[Quinc]

be careful and make sure you are not actually overheating.

This^ Blow out your waterlines and run it with the hood off to make sure you have water going through them. You should be able to splash some water on your engine and pipe and it shouldn't sizzle or steam off right away.

 

[pos109]

Ive had this same exact issue with my SN. Start start switch was acting up causing a condition that resembled over heat limp mode. Unplugged the start stop and issue went away!

 

[naticen]

I'm going to make some time to knock it out this weekend. It's my girl's ski, but we had a couple others to make it through last weekend.

 

[CRJ]

check your cooling line isnt plugged. sand and crap clog lines quick.

 

[naticen]

I unplugged the sensor on Sunday, capped it real good, and it did great for about 2 hours or so and then dropped back to barely planing whether half or full throttle. Engine and pipe are not anywhere near sizzling water. Left it sit for 20 minutes, fires right up, although still barely planes and ride back for 2 miles to the .75 mile no wake and took it home. I'll have to do some more fooling around. Luckily it's the backup ski and the other 2 are running good. Unluckily, I've got multiple other skis to take care of and it'll probably be another couple weeks before I touch it again.

 

[BIG JOHNSON]

Ignition coil that is failing will work fine when it's cold, then sporadic when engine compartment warms up. I have a known to be good spare coil and wires if you need to use it to diagnose. I'm in Charlotte.

Edit: I had similar problem when I had my 750, but it would only run well for the first 15 minutes then hit and miss.

 

[naticen]

I appreciate the offer but I've got some extra parts. What I need is extra time, if you have some of that I can borrow. Part of it is procrastinating touching that ebox. I hate Yami eboxes

 

[hesty32]

Naticen, did you get this fixed? I've had two similar symptoms that looped me for a while. Not exactly like you describe but pretty close. Maybe they will give you an idea.
One was an engine bay exhaust leak. Ski would fire up and run great for 15 min then acted like I could only get 1/3 throttle. Eventually just had to run it with the hood off (carefully) for 15 min. Then put the hood back on and it would "limp" after 15 min. Finally found a leak in my fiberglass water box seam. Couldn't see the exhaust smoke in the engine bay but the cracked seam had oil n soot running out of it. It was on the front side though, didn't see it until I removed it.

The second one problem was a shorter time before the from start to acting up but the time varied. A cheap external fuel filter element had come loose and my internal carb screen had clogged up. Trouble shooting for that was pump the primer plunger when it started limping and see if more fuel helps = probably a fuel issue not electrical.

Hopefully this is all moot though and you've got it fixed already!

 

[naticen]

Not really figured out yet. I decided to get it running for Daytona and just swapped out the entire e-box for another one that was good from a seller although never tried personally. When I went to start it, the Start Stop Switch wasn't working. I swapped it for another good according to the seller switch and took the ski untested. It ran great for a few hours Saturday and then another couple hours Sunday until it started doing the same thing again. Still not sure what's going on with it and I have at least one ski and hopefully two to build before WaveDaze, so it'll probably sit for another few months before it is touched again.

Mine is totally random whether it'll act up within minutes or hours and will not change when ridden with the hood off, so I don't see it being exhaust. Also the plunger won't cause any unexpected changes to it running. I would definitely put money on an electrical problem although I do appreciate you looking out.

 

[hesty32]

Yeah that is sounding electrical I guess. Well I'm no pro but I thought I would offer the little bit I know. Good luck with it! Sounds like its going to be full electrical trouble shooting, testing the wires and everything ohm-ing out everything! Those problems are frustrating! I have a trouble some SN but it's on the back burner while I build a new hull too.

 

[mthomps]

Hey man my season ended with pretty much the exact same problem that I'm still troubleshooting. I have a video from my thread I'll try to find so you can see if the "limp mode" sounds similar to mine. Mine sounded like it would start to run on one cylinder.

My superjet is a stock 650 and I tried everything electrical. I repacked my perfectly good coil with new wires, then tried a friends, swapped cdi, disconnected the pink heat sensor wire, checked all fuel lines, one way valve, drained my gas, checked for exhaust leaks ...all the usual crap.

Now I'm convinced its a carb problem.

 

[mthomps]

I forgot to add mine starts up in and out of the water with one bump of the start switch and will run all day limping around. The problem comes on right after idle for me.

Does yours sound anything like this?

 

[naticen]

Not quite. Mine would only do it under load. If you beach it, it will instantly rev fine all the way to the rev limiter. Even in the water it's not really breaking up like that. I sold it to a buddy that has more time for it so hopefully he'll knock it out soon and I'll update what it was.

 

[Noah701ski]

Not quite. Mine would only do it under load. If you beach it, it will instantly rev fine all the way to the rev limiter. Even in the water it's not really breaking up like that. I sold it to a buddy that has more time for it so hopefully he'll knock it out soon and I'll update what it was.

My FX1 does this aswell it has a bad crank seal, pretty certain that isn't causing this issue. Did your friend ever figure out the issue on that superjet?

 

[naticen]

I don't remember that well almost 10 years ago. I know we rode together more after that so we musta figured it out. Got sold again about a year later so it's long gone now.