I have a 1997 Seadoo GTI. Same 720 motor. On the bottom of the exhaust manifold underneath is a water bleed line . it continues towards backside of the hull to a T in the hose. The T now divides in to two hoses. One goes to the exhaust, the other to the outside weep hole below the back of the seat out the back letting u know water is flowing through the cooling system . Pull the hose off at the T going to the the Bottom of the exhaust manifold. Blow in to the hose . Sand and build up can clog the narrow outlet connector not allowing water to drain out through the weep hole, and exhaust. Or this, the 2 main cooling lines in the inside center back of the haul that go to the back top of the motor head are reversed. When u look at the head where the hoses go in you'll see arrows indicating the direction of the water coolant flow. Look close you'll see them. The one hose closest to the center of the inside back of the hull is where the Jet pump sends water to the left side of the head as u look forward to the front of the Jet Ski. The other hose further out to the side is the flush hose that a garden hose that gets connected to on the outside of the Jet pump. . If those hoses are reversed water won't come out of the weep hole to let u know water is fully properly in the right direction circulating through the cooling system. Fortunately on top of the motor head is a Temperature sensor that has a wire connected to it. If the motor cuts out and you hear a long continuous beep, it's either the motor over heated or a bad sensor. They can go bad occasionally. A Big time problem with the 720 2 stroke motor is the Head pipe loosening where it connects to the top of the exhaust manifold. There's water jackets in the head pipe and exhaust manifold on each side of the exhaust. Water enters causing a rough idle or the motor completely shuts down. I had to take the manifold to a machine shop and have what are called stainless steel Time Serts put in held in by epoxy. There's helicoils standard in all the bolt holes in the completely aluminium Block exhaust, etc. They back out easily when unscrewing a bolt or work out from vibration. 2 stoke motors have a lot of high frequency vibration. It was a constant problem until a mechanic told me how to fix it. I suggest you down load a shop manual on the Seadoo forum or buy one on Amazon. The 720 motor is a great motor, A lot of guys get 400 hours out of them or more. New cylinder compression is 150 psi. Seadoo dealer told me when the compression hits 110 a rebuild. My mechanic says 100. There can be as much as a 10% compression psi difference between the 2 cylinders. My 97 GTI has 146 and 135 PSI during a recent compression test. Plenty of life left. You must use Seadoo's 2 stroke mineral based 2 stroke oil. TC3 Blue 2-stroke oil will screw up the motor according to Seadoo. There's a waring note about it next to the oil fill cap. It comes in a Black gallon container labeled for snow mobiles. Ignore the not for out board use. Or else pay $25 more a gallon for synthetic 2 stroke oil u don't need . The 787 and 951 motors gets synthetic. Good luck and message me if problems occur. A Stupid Seadoo mechanic had those cooling lines reversed, good thing I knew what I was looking at.
