300/440/550 not shooting out whater when in the water

[axion515]

89 js550 got it from my uncles yard..did some some work and it runs awesome for 20yrsold. starts up one push and doesn't shut off. but when i have the garden hose hooked up to it water comes out of the exhaust and the pisser..but once its in the water it doesnt pull in water and keeps over heating....this is my only problem with my free jetski...so if anyone can help me narrow down the problem please help me out!

 

[AtomicPunk]

you have a shell our some sand blocking the cooling line between the pump and the motor.

Pull the cooling line inside the engine compartment where it connects to the motor and blow some compressed air back down that line towards the pump.

 

[djkorn1]

or blown head gasket