Welcome to the seadoo forum Jack. Is it possible that the battery doesn't have a full charge? If it is it could be that the starter isn't getting a good ground or power. Check the ground cable to the starter and the power wire feeding the starter. If both wires look ok, open the box that the red power wire that goes to the starter is. Inside is a solenoid. Take a 14 guage insulated wire and jump(Quickly)across the two heavy wires at the top of the solenoid. The starter should turn over. It is possible that the starter is bad and that was the hum you heard. If it doesn't turn the starter over it might need a starter. Before you pull the starter out, go to the back of the engine. Loosen the clamps on the black boot and slide it off so you can see the shaft. Remove the spark plugs, and put the spark plug caps on the grounding studs. Grab the shaft and see if it turns by hand. If not use a pipe wrench to see if it turns over it should turn over counter clockwise. Be carefully not to hurt you hands or break something. If it does turn over than it isn't seized and might be the starter. If it appears to be seized and won't turn over it's time for a tear down. Let us know how you make out up to this point and we'll go from there. There is a lot of information here for you to do. take your time and keep us posted.
Karl
