I had the same thing happen a few years ago and we determined that we hit something submerged and it caused the props to stop and that caused the shaft to back up, shearing the gears and the shaft popped the cap off. We had to replace both drives because it was more cost effective than replacing all of the parts (labor + parts). Whoever you take it to they need to convey that to the ins. company. State Farm paid for the new units minus deductible. GOOD LUCK!