I have a 2000 Genesis carbureted. It has always run and performed great with no issues for the 4 years that I have owned it. Last year I let a friend ride it while we were at the lake. He took off too close to the beach and sucked up some sand. Within just a few minutes the over temp light came on and it went into limp mode. He is not the brightest person and kept trying to get it to go not paying any attention to the flashing light and over temp warning. I was lucky that the sand only plugged the exhaust cooling screen. It melted the exhaust hose from the manifold to the exhaust can and both of the plastic resonators. When the exhaust gases filled the engine compartment the engine quit. Over the winter I replaced both of the plastic resonators and the exhaust hose. I removed the exhaust water injector screen and cleaned it. This spring I put it in the water and started it without the hose for the injector connected and made sure that water was flowing to the exhaust. The ski ran great with no issues the next couple of times out. I was riding it with my wife the next time we went out and after riding for over an hour it started running bad. No warning lights over temp or any other signal. It finally quit totally when we reached shore. I removed the seat and the engine compartment was full of exhaust fumes again. I checked the engine with my hand to make sure it was not overheated. The engine would start and run with the seat off but would fill with exhaust fumes. My first thought was that an exhaust clamp had loosened and was leaking. Back to the shop for a look see. The hose clamp on the plastic resonator on the right side had come off. When I removed the hose to re clamp it I noticed that the tube on the resonator that the hose clamps to had melted and collapsed. I removed that resonator again only to find that not only had it collapsed but 2 holes had melted thru the side of the resonator. I also noticed that the inside of the new exhaust hose that I had replaced had little blisters the size of your fingernail on the inside. The only thing I could think of is that I picked up some more sand in the exhaust water injector screen. I order a new resonator and took the screen out again. The screen was clean with no sand. My next thought was maybe I picked up some weeds or something while I was ridding. I checked the cooling inlet and found nothing. I pulled the intake hose off of the thru hull fitting and connected to the garden hose to see if it was plugged. When turned on I got water out of the little injector hose as well as out of the engine output hose below the stat. No clue what caused the over temp exhaust. I got the new resonator installed and took it back to the lake. Again I pulled off the exhaust injector hose when it was idling and water was squirting out. Put it back on and rode it very gently for about an hour with no problems. Problem solved right? Wrong. My son and his wife and my grandson decided to take it for a spin. They made it about 1/2 mile out and it started running bad again and i had to go get them in the boat. When we got back to shore and removed the seat there was the exhaust fumes again. At this point I was about to tow it to the middle of the lake and sink it. Back to the shop only to find the same right-hand plastic resonator had melted again. I ordered another one and began brain storming. I thought that maybe the first time that it got sand that maybe some sand had partially plugged some of the ports leading from the block to the exhaust manifold and was not allowing enough water to flow the exhaust for proper cooling under a load. I removed the complete exhaust manifold and exhaust can (the log). No sand nothing not even a single spec of sand. I connected the garden hose to the water line the connects to the exhaust log and ran water backwards out of the water intake hoping to see something come out of the input line. Nothing just clean water. I have replaced the resonator again and re assembled the manifold and all of the hoses back on. It starts and runs great on the trailer with no leaks. Needless I am a little leery of doing the same thing again any help or suggestions would be great.