Kawasaki jet ski - loss of "top end" power.

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We have two jet skis, had them out yesterday for the holiday.

Last fall, I prepared them for winter, as I always do. While getting the Sta-Bil Marine formula throughout the fuel system, I took them out for a final 10 minute ride in some really cold water. Both ran fine.

However, this year, the Kawasaki TS550 is having a problem. It runs smooth at all RPM's and starts fine, but it doesn't have enough power to get itself on "top" of the water.

Checked the impeller for weeds, nothing.

I checked the sediment bowl for water or dirt, found nothing. While the bowl was off, I pumped a some gas through the line (using the primer bulb) to see if it was able to get a good flow of fuel from the tank, and it flowed fine.

I took the air intake off above the carburetor, and the screen on top of the intake was clean. Looked down the throat, saw nothing but clean. I was thinking that if something (a mouse) had gotten into the air intake (or the air box) somewhere, that the screen would NOT be clean, and that would be a sign to tear into the air box. I wasn't in the mood to go that deep with it sitting on the water.

I still plan on checking the air box, just in case.

If I had to guess, it isn't getting enough air.

Where else should I be looking. Other than not having enough power to get it "on top" of the water, it runs fine. It doesn't miss, doesn't smoke any more than it should, and starts fine.

???
 
Originally Posted By: hate2work

What kind of exhaust system is on a jet-ski? Sounds like it could be partially plugged.


The entire unit is bone stock.
 
Originally Posted By: Scorch
When was the last time the plugs were replaced?


Not since I've owned it. Why plugs?

I'm skeptical that the plugs in both cylinders would somehow happen to fail in the same way, at the same time. The only way I could see that happening is that the fogging oil did it.
 
Does it have any sort of variable intake or fuel system on it?

A very generous co-worker of mine let me keep his Yamaha Waverunner XLT800 at my house over the fall/winter/spring a few seasons ago, because he never uses it but in the dead of summer. The craft was fast enough, but I didn't realize how fast until after smacking down on the water after a jump only to have it gain about 10 mph and another 20 horsepower (or so it felt like).

There was a power valve on the engine that must have been stuck/gummed closed. The engine would max out at about 6,500 rpm as I recall and exactly 52 mph. After the power valve loosened back up and opened as it should have, the engine would max out at around 7,200 rpm (again, as I recall), and I'd get exactly 62 mph out of it.
 
Originally Posted By: mrsilv04
Originally Posted By: Scorch
When was the last time the plugs were replaced?


Not since I've owned it. Why plugs?

I'm skeptical that the plugs in both cylinders would somehow happen to fail in the same way, at the same time. The only way I could see that happening is that the fogging oil did it.


This year my Honda Aquatrax R12 was running perfect when I launched it, put her in the hoist overnight and the next time came out to ride. Eased into the throttle and by the time it hit 35 there was nothing left. This is a machine that easily pulls 65mph on calm water, did a little research, a few sites said change the plugs so I started there and it runs like new again.

If I don't change the plugs in my 2 stroke 600 snowmobile every year I end up with bog and loss of top end also. Something to try?

And in response to Hokiefyd that would definitely make sense if this engine has powervalves, get some new gaskets and pull them out, soak in MMO/Techron or use steel wool and some carb cleaner to clean them up, they definitely cause issues in snowmobiles so I'm sure it would apply here.
 
Last edited:
Thanks Scorch.

For $6 (for two NGK plugs), I'll give it a try. Even it it doesn't help, that will then be "off the list".

I'm also tempted to add some Sea Foam or MMO to the gas as well.

This unit is from the early 1990's, and is really quite simple. I don't even know if this unit has powervalves or not. I'll have to do some research on that.
 
I was going to suggest plugs, plug wires or anything ignition related. There could be enough spark to start and idle, but once you put a load on it, it won't go.

Like you and others have suggested, starting here will at least get it off the list of suspects.
 
OK, I'll take this a step further. I have no idea as to what brand of spark plugs are in it right now.

Off hand, my first choice for replacements would be NGK's, as I tend to choose NGK's for the motorcycles.

Agree?
 
I hope there is not a lack of oil. I've had a couple of ski's seize up due to failed oil injection systems. My SeaDoo SPX had the cable pop off and the engine got idle oil levels only. It bogged down like something was wrong with the carb. But it was lack of oil.

My Yamaha had the oil line pop off. Same thing, but that one locked up.
 
Had a similar problem with my 1998 Sea-Doo. Turned out to be the wear ring. I was inspecting the impeller to see if it was damaged (couple of small dings), and noticed two big chunks missing from the wear ring. Apparently that caused enough lack of propulsion to prevent the ski from getting up on plane. Replacing the wear ring returned the ski to like-new performance.
 
Originally Posted By: Scorch
When was the last time the plugs were replaced?


Scorch nailed it. I picked up a couple of NGK plugs at Advance Auto Parts for $1.89 each. Put them in, and it runs great again.

I'm pleased!
 
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