
While staying PC, Personal injury would be the biggest, and the biggest claim if you ever had one. Trust me they make boats look cheap.
Comprehensive, Act of god, whatever. Ins company would never know, nor would they really care "probably" care, just cut a check for agreed value(being original).
But yea if you caused say an accident and you had altered the boat from its original status (insured capabilities), I am willing to bet on a Liability they could deny claim.
Liability claims are the ones that bankrupt people, you know like death, injury, greedy lawyers.