I went in halves on a 79' sea ray that needed some interior TLC and new ball gears. The guy I went in halves with replaced the ball gears but accidently ignored the part about using locktight. It ran like a champ for about four hours on the lake everything worked great, temp was good, no noises. Then out the blue it made a clunk and the engine died.Fearing an engine issue I towed it back to the ramp to find the gear from the drive side missing the nut and the recieve side about to fall off with a large indintation in the ball gear guard. The motor runs fine stiill and the prop spins free.Any ideas? or is it possible the ball gears bound up.Oh and the ball gears had significant wear for that been there only trip.