I was on the Parker strip circa 1991 when someone's boat was stolen from Sundance. Allegedly the boat was shoved off and floated down river while the thieves stripped the blower and induction. The boat was later found on the rocks, minus the induction.
This has always made me paranoid about my own boat. Thieves don't need to know how to start it to tow it off. When I attended the Hot Boat Regatta at Irvine Lake, proof of insurance was required. I contacted the same lady at AAA who insured my boat for the previous owner, she said, "NO WAY!" Wozencraft was the only carrier who would insure my boat, they would not put a value on it without receipts for anything. Regarding speed and horsepower, I played dumb. Wozencraft was kind enough to fudge the numbers enough so that I could be approved. What I learned from all that is 1. the insurance that I pay for is not to protect me, it is to protect others if I make a mistake 2. if you can't document that you had it, even if it is in the pictures, the insurance company is NOT going to replace it 3. deviations from what is acceptable is grounds to deny a claim.
Bottom line, keep good records! And YOU are the last in line for the safety and security of your passengers and vessel.