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Yikes! Something broke, don't know what or how to diagnose!

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Michael211_2000

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Well I took my 2006 RXT to the lake this afternoon and though the lake is getting low I was able to walk it out past the boat launch and piers to deeper water and take off (by next weekend, it's going to be too shallow to launch even PWC's anymore, we're so DRY here!). The water at the boat launch was about knee deep, deep enough to float the hull without touching bottom but not deep enough for me to get on and start the engine so I walked it out to chest deep water about 30 yards out.

So the water was absolutely perfect today, almost no wave action at all (and no boats on the lake either, just a few other PWC's). I decided to try opening her up to full speed finally, got up past 60 mph, then to 65 mph, then 67 mph, and suddenly NO POWER! I thought the engine had completely died, but as it slowed back into the mid 30's I felt the engine was still running but very erratically and no power whatsoever. WTF?

Since it was still running and not making any bad mechanical sounds, I pointed it to the boat launch and made a B line back there (stopping far out, before the water got too shallow). The whole way back the engine was surging badly and it was taking WAY too much throttle to get it to go... it felt like either it wasn't getting enough fuel, or 1 or more cylinders was cutting out. It never died though and there were no alarms or codes on the display (so the sensors all think everything is peachy I guess). Before walking it thru the shallow water to the launch, I killed it and floated around for a few minutes in 6 feet of water then re-started it (it started right back up easily!) and tried a big power circle.. it was still missing and surging and all, something is definitely wrong here! I killed it and put it back on the trailer.

I got it back home on the trailer and before sunset I checked the Supercharger and it's fine the air impeller wheel cannot be turned by fingertips and there is no oil residue in the intake hose. I also removed the seat bridge, pulled all 3 ignition coils and all 3 spark plugs... everything looks fine, the plugs are not fouled or anything and none of the electrodes appeared "wet". I put them back in and put the coils back on and that's how she sits tonight.

What next? I started it on the trailer and it is evident to me that the engine is running rough and surging a little at idle on the trailer. I'd guess the timing chain isn't broken or else it wouldn't run at all. It didn't drop a valve, that would make noise and alot of it I'd think. So what's wrong here? I'm not sure what to check next guys. The fuel is fresh, it ran just fine for almost 30 minutes until I opened it up for that high speed run... that was the first time I've gotten it into the upper 60's and it was still accellerating before whatever it was happened. I'm mystified.

Could the timing chain tensioner have failed possibly letting the chain have slack throwing the timing off randomly? I'm thinking of pulling the valve cover in the morning and checking the chain for tension unless somebody has a better idea. The surging and missing is not consistent, it's like random and comes and goes and she starts with just a bump of the Start button but idles rough like it's missing. IDK. I'm thinking this isn't a catestophic failure but it's not obvious what it is either. At least it got me back to the launch safely! LOL!

Help?

- Michael
 
Start with a new set of plugs and do a compression test and post the findings A wot run should not hurt your ski I run my ski hard and that the way they are made to run or they would not let them run up to 8k rpm
 
Start with a new set of plugs and do a compression test and post the findings A wot run should not hurt your ski I run my ski hard and that the way they are made to run or they would not let them run up to 8k rpm

These plugs only have 5 hours of runtime on them, and all 3 look pristine. I don't have a compression tester but I guess my local auto parts store should have an inexpensive one. What reading should I have on the cylinder's compression? I can do this later this afternoon.

Thanks!

ps. I'm at 74 hrs, the SC washers have been changed out with steel washers, and I was running 67 mph @ 7400 rpm when I lost power suddenly.... no strange sounds or anything, the engine just suddenly seemed to stop running like I'd turned it off (though it turned out as I slowed down that it was still running but just barely).

- Michael
 
These plugs only have 5 hours of runtime on them, and all 3 look pristine. I don't have a compression tester but I guess my local auto parts store should have an inexpensive one. What reading should I have on the cylinder's compression? I can do this later this afternoon.

Thanks!

ps. I'm at 74 hrs, the SC washers have been changed out with steel washers, and I was running 67 mph @ 7400 rpm when I lost power suddenly.... no strange sounds or anything, the engine just suddenly seemed to stop running like I'd turned it off (though it turned out as I slowed down that it was still running but just barely).

- Michael

yeah michael i dont think that plugs are your issue here so i wouldnt worry to much about that!! Well..... you know the drill , first get a compression reading and report back and we will go from there.
 
I've never actually done a compression test on any engine, automotive or marine. Never had a reason to, problems in the past have been pretty straightforward to diagnose on my engines. Guess I'm going to learn something new here today! LOL!

I guess I'm taking this pretty well since it looks like our boating season is essentially over here... all the area lakes are getting too low to launch/retrieve boats at this point. My favorite lake, Lake Livingston, has been holding up pretty well because it gets most of it's water from the Dallas/Ft Worth area of Texas and they got more rain this spring than the Houston area did, but now even it's getting too low to use. The weather forcaster on TV just now said he doesn't see our weather pattern changing significantly until the middle of September at best.... yikes!

So, looks like I have plenty of time to figure this thing out. That 67 mph run, though short, sure was FUN though!!! Wow that's fast on such a small watercraft! My jetboat however goes up into the mid-80's and it's like flying across the water you don't even feel other boat wakes as you go across them. :-)

I'll get back here with the compression readings later this evening if I can get a compression tester this afternoon. I appreciate any/all help on this issue! Thanks!

- Michael
 
ok michael since you have never done a compresion reading ill explain it....... It relatively simple just find a guage and pull out one of your spark plugs (leave others installed like normal but remove the plug wires off them) then screww in the compression guage where your plug was and groung the plug wires so they dont catch anything on fire...... then hold your throttle wide open and hit start and roll it over till the guage stops moving (about 3 seconds) do the same for all the cylinders and report back the numbers
 
Ok why do I need to ground the plug wires again and how? If they're not connected to anything, no current should flow thru them right? Seems like laying them aside where they aren't touching anything metal would work... or am I mistaken?

Why do I need to hold WOT? I know that keeps the engine from starting when the plugs and coils are installed, but with the coils off the plugs it can't start anyhows so....

Please advise. Thanks.

- Michael
 
holding WOT gives the ski the maximum compression and will show a higher number on the guage you dont have to hold it WOT if you dont want it just helps give it the best reading and as for the plug wires they need to be grounded because the current will still flow and it will jump to a ground (the engine) and can cause a fire if you have anything flamable on the engine or any vapors..... as for grounding the wires there should be grounding posts on you e box somewhere or they could be somewhere else in your ski just check the manual and it will show you where they are...... if you want to try to do it without grounding the wires you can just do it outside and make sure you take off the seat and let it air out for a while.... But i really dont advise doing this ive seen many ski melt down in a ball of fire from not grounding the wires and the arc causeing an explosion
 
Wow! :-O

Mine doesn't have any grounding posts though, no such thing is even mentioned in the owner's manual and I put the engine in my hull myself last Fall so I know there's nothing in there that looks like 3 spark plugs to mount the iginition coils on. It has however been sitting outside in my front yard under a shade tree with the seats off since I got it back home yesterday evening (ie. it's very well aired out at this point!).

If the coils are kept far away from any metal objects they should not be able to arc, I would think? Voltage may go to them as I crank the engine over, but if they're an inch or two away from anything metal they should not be able to arc across... or am I mistaken on this?

Ok the WOT info is good to know then. Thanks for the explanation, I never read that before.

- Michael
 
glad you understand the WOT thing it just lets the maximum amount of air flow throught the engine and gives you the most accurate reading. As for the grounding posts IDK maybe your ski dosent have them mine does so i thought that amybe yours would but i would think that your ok if you have been letting it air out just check the compression and let me know what you find so we can fix this and you can go ride on your beautiful lakes LOL
 
Problem: I went to local auto parts store, they had 2 compression testers... #1 had a hose attached to the guage with threaded fittings, but none were the same size as my spark plugs (I took 1 of my plugs with me to be sure!), while #2 was a rubber-tipped push-in style guage but it was far too short to reach the spark plug holes AND it had a 45 degree bend in it's rubber tip so no way it would have gone down those plug tubes on this Rotax 4TEC engine.

Can someone please recommend a guage I can buy to test the cylinder compression on this engine with? Automotive compression testers don't appear to be feasable.

I went ahead tonight and pulled the valve cover off and checked the timing chain. It looks fine, I can see the tensioner and it's plastic guide it pushes against the chain and I see the other plastic guide on the other side of the chain... it looks just like it did when I installed it last Fall. Everything on top of the head looked fine in fact, what little oil was left up there is clear and clean, and I checked the engine oil level via dipstick and it's perfectly in the middle of the bend on the stick.

So..... I'm stuck now. I need a compression testor that will work with this engine.

Oh, and about the ignition coils why not just unplug them and set them aside? They do have connectors after all, I'd assume without being plugged into the coils the connectors would not have any risk of spark at all! :-)

Thanks!

- Michael
 
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2 things....1. my grounding points are on the black box next the battery..2 silver prongs sticking out on top.
2. Try Sears for a craftsman tester. That what I use for BR8ES plugs. There are 2 thread sizes on this tester. Some K-Marts carry Craftsman along with some ACE hardware stores.
I would stay away from the rubber tips ones, they are tough to get a good reading.
 
If your engine is a 3-cylinder 4TEC, why does it only have 2 silver prongs for grounding points? I don't think you have the 4TEC engine, buddy. The year models you have listed in your profile I do believe are all 2-cycle engine models (mid-90's models). I'm not sure when the 4TEC engines came out though, so I could be wrong.

Besides I'd have to cut the wiring harness up into pieces in order to move the 3 ignition coils anywhere at all, there's only 2 or 3 inches of wire running outside of the wiring harness to the coils. I think simply unplugging the coils and setting them aside will be more than sufficient to prevent any sparks.

I guess I'll take the spark plug to Sears at the mall and see if they have a tester with the same size threads... that's going to be pricey though I bet. :-\

- Michael
 
I didn't mean to imply that I have the 4TEc engine. I have the 787. I was just saying that my grounding points are at the box.
 
I didn't mean to imply that I have the 4TEc engine. I have the 787. I was just saying that my grounding points are at the box.

No offense but what you're pointing out is confusing the heck outta me since you aren't talking about the same engine! I'm concluding that the 4TEC engines don't have grounding points for the ignition coils, since the coils can be completely removed by unplugging them from the wiring harness.

If you don't have or know the workings of a 4TEC engine then you're not helping me here you're just confusing me. LOL! At least say "On my 787 engine the grounding points are at the box" so I know you aren't referring to a 4TEC. The 4TEC is alot different than your 787.

Again, no offense but ya'll are confusing me with info about other engines while not telling me that you're referring to other engines and not a 4TEC engine! What your engine has is not necessarily the same or even similar to the 4TEC engine. I don't know exactly what year model the 4TEC engines came out in, I don't even know if a 787 is a 4-cycle or 2-cycle engine or how many cylinders a 787 engine has for that matter.

I appreciate the attempt at being helpful, I really really do!

- Michael
 
Back up the bus here a moment. There are no grounding posts. Those are on 2 strokes. You've received a lot of good info but you don't have a 2 stroke!

Just for me, put a NEW set of plugs in it before you go down any more roads. These are the least expensive items that are the highest failure on the 4 strokes and you can't tell if one is bad or not just by how they look. One could be fouled with no visual signs of anything wrong. From your description of your problem, it sounds very much like you have a fouled plug.
 
Now you say the plugs have only 5hrs on them it makes me think they are more Likely your problem if your ski ran fine all this time now you throw a new set of plug and a few hrs later it not running right it usually the last thing you touched please replace the plugs what a plug looks like don't say much if it fractured internal you can see it (unless you have x-ray vision lol) cheapest and easy thing to try and rule out and at worse case you have a new set in for next season nothing to lose
 
I think the regulator would throw an alarm if it were the acting up. If yo change the plugs and problem still exists, check your coils. Did you have fresh gas in it when the problem occured?
 
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