hey guys, trying to find out what the problem is with this kawasaki 1100 di, its beyound my repair expertise.

i work on jet skis on the side but this is my first di ive ever encountered. lemme tell you what ive done and what ive found so far.

a customer brought me his ski and said it wont go over 40 and use to be much faster. hes never done any maintenance on it what so ever.

he brings it to the shop and i pop the seat to find a melted exhaust coupler between the exhaust pipe and waterbox. the entire ski was coated with carbon and varnish on the inside from the exhaust fumes being inside of the hull. i then assumed i knew exactly what the problem was and relaced the coupler and sent it back.

well a couple days later he calls and said, it still wont go over 40 and brings it back to me. i take it to the lake to do a lake test and sure enough. it wont go over 40. the engine is strong and hits 7k w/no problems. runs exactly like its cavitating but ive already checked that and all is well. after about 2 minutes of riding, the skis exhaust note gets really loud and then dies. when i stopped i saw smoke coming from around the seat and could smell melter rubber so i popped the seat to find the waterbox was super hot and melted the rubber couplers connected to it and the plastic strap holding it down as well as the plastic resonater behind the waterbox.

so i take it back to the shop and start pulling the waterbox out and found the insides were in a million pieces. it was filled with pea size pieces of aluminum and was like it was shattered. i flushed the coolant lines and found a june bug plugged in one of the line. so i replaced the entire system with a good used one and put it all back together and gave him the ski and told him what i found.

well he called me back about a week later and said the ski still wont go over 40 and its starting to melt the rubber couplers again.

compression is great on all 3 cylinders, impeller to wear ring is perfect according to the eye, looks very tight, it does have a swirl impeller??? dont know if thats stock or not.

so, when i ride the ski, it will rap out and hit its rev limit but only go about 40mph. i can tell that theres way more potential. theres no signs of cavitation because theres no air bubbles what so ever and after extended wot runs, the exhaust gets super hot and starts to melt the couplers. when i say exhaust gets hot, the engine and exhaust pipe are normal but the water box is super heated.

i dont know much about di's and hope like hell someone on here might help. ive done a little research and found that they have computer problems. do you think thats whats causeing the hot waterbox?