Boat motor won't turn off !

there should be a manufacturers plate attached to the hull of the boat with a number of passengers it can carry and the max hp motor allowed to be fitted
talk with boat shops as they will know the approximate hp for each make of boat and length
while it may be attractive to fit big hp motors to small boats , it in fact makes the boat less sea worthy and makes capsizing easier so get the advice right from the boat shops

Maybe running hot

I'm sorry but you have this posted in the wrong product category. Please re-post the question in the proper category This is the car and truck problem category

check your thermostat is working ok.

Check the running height of the motor.The prop shaft should be about one inch below the straight line of the bottom of the running bottom of the boat.With a cleaver prop it may be lower.A chopper prop is the best and you can run every bit of that.2 inches if pitch is = to about 500 revs.Try a few props 1st before you pay the dollars for a new one.The bouncing is the wrong transom height and prop.You don,t need a cav plate if the boat is set up right.(a cav plate extension like a manta).Bad dealers may want to sell you these.A well set up boat doesn't.I've set up and run a lot of ski racing boats and all have never needed any "bolt on parts".Its mainly a motor height and prop selection thing.Hope this helps

Check that the ignition swith is grounded.

power supply for the radio taken from a source wire that is affecting the voltage regulation
take it in or have a radio technician come and check the installation

not enough information on the motor. what year and model? but all yamaha outboards are shut down by the C.D.I. being grounded by the key switch or the emergency kill switch. the cheapest thing to test or replace is the key switch and the emergency kill. with more info on engine I can help you further.