1997 Kawasaki 1100 STX runs slow in the water

[Eric4509]

I have a Kawasaki 1100 STX and It was tuning great until this week I went out on the lake and for the first 15 min it ran great but then while at full speed it started losing power and slowing down until it died. I got it started back up but could never get it back up to speed. At full throttle I get 4500 rpm and get max speed of 25 km.hr.

I took the ski home and while I was flushing the motor I found that I could rev it up and it sounded fine getting full throttle 6-7k rpm.

When I removed the three spark plugs I found the the cylinder closest to the front of the boat had no gap at all. Changed spark plugs and fuel filter, went back on the water and even though it would run it still would not go fast enough to get up on the water.

I am running non-ethanol fuel pre-mixed at a 50:1 ratio.

The Jetski was running great and any help you can give would be great.

 

[Jeff Walkowiak]

Bad rod bearing, it is ready to blow, do not run it anymore. the gap is gone because the piston is hitting the end of the plug.
Remove the plugs and rotate the engine by hand, watch inside the cylinder that is giving you a problem, as the piston comes to top dead center it will start to travel downward as soon as it starts to go down, stop turning the engine place a screwdriver in the plug hole then push down on top of the piston if you hear it clunk or feel it clunk that is play in the rod bearing or wrist pin bearing but either way it's time for a rebuild if you don't stop running it you will do a lot more expensive damage to the engine so cut your losses.

 

[Eric4509]

Thank you Jeff for taking the time to let me know. I don't feel experienced enough to do this myself so I have taken it in to a local marine mechanic for him to rebuild.

 

[Jeff Walkowiak]

I promise you by doing that and not continuing to run the engine you saved yourself a lot of extra damage and expense.