I have searched and found no answers so Im really hoping for help. My 89 js550 runs great!!! The only problem is that it only runs great out of water. In the water it will get to mid rpms, and when i make an attempt to plane (go WOT) it will slowly get on the plane and then shuts off. It always starts back up easily but when I start it back up it will just idle. I'll be WOT and it will just be holding an idle. A few minutes later it will repeat the process all over again. It act's like it is going to plan, but then shuts off. When it shuts off it sounds and feels like it would if you let go of the throttle. Even though you are holding WOT. It has fresh gas with good oil at 40:1. However on land it runs great. I have tuned the carb perfectly (imho) and i am confident it is not my tuning. It is a stock Js550 other than a pipe. I have taken off and cleared my cooling lines as well. The best way I can describe it when it gets on a plane is its hitting a rev limiter like a car. Basically stuttering. I disconnected the RPM limiter on the ski and the problem is still there. I have not checked compression but it always starts very strong and runs and sounds good out of the water. As i am new to jetski's im not sure on what is normal and what isnt. My exhaust is smoking dry out of the hull. Is it supposed to do this? Or is water supposed to come out with it? On land when it is hooked up to the hose water comes out of this. But I didnt notice water out of this in the water. Im thinking that may just be because im not able to run WOT and the engine isnt running fast enough to push water out of the water box. I have installed a new water box as well. My ski is also equipped with a primer. (trying to add as many details as possible.) So basicly im curious, what could be causing a ski to run good on land, but not reach its full rpms on the water. Thanks so much for the help.