What causes overheating on a Seadoo Sporter? Or in a jetski?

I have a Sportster 1800 and the overheat alarm keeps going off... What part wears out that causes it to overheat? I flushed the engine before we went out then it over heated.... The engines are the same as most of the jetskiis.|||Jet boats and jet skis don't have water pump impellers like outboards. They have a takeoff in the jet pump that diverts water to the head. That takeoff could be clogged, the hose could be clogged with pebbles or weeds, or an outlet could be mucked up. Look for a hose coming from the pump housing to the cylinder head, and start there. It should be the same hose as you flushed it with. It that's all free, look in the pump housing for obstructions.|||most likely cause: worn water pump impeller. not the jet drive impeller.





If you're in the habit of starting the engine while the boat is out of the water, you should be aware that it only takes about 45 seconds of dry running to damage a water pump impeller.





Other possible causes: worn water pump housing gasket, thermostat corroded or worn out, blockage in cylinder head water jacket, cooling water intake blocked, timing needs adjustment, lean mixture (air/fuel ratio too high) due to clogged/partially clogged hi-speed carb jets or fuel injectors, inadequate oiling. There are probably others.





You really should stop running the engine until you've pinpointed and corrected the problem - when an engine overheats, the pistons and rings expand, scoring (cutting grooves in) the cylinder walls. Scored cylinders loose compression; lost compression means lost horsepower.|||I don't own a jetski but I've heard that the water inlet may become clogged with seaweed or other floating debris. Have you checked to see if the jets are clear?|||Check that the water intakes are note clogged. My seadoo's alarm would always go off if I was going to slow (It was not getting enough water).