At the same time how can you expect a business to fix something because of a change in fuel which was completely out of their hands??
Thats like saying 10 years from now if you bought a 2015 Gas powered vehicle and in 2020 gas no longer existed and electric cars ruled the road. And you want Ford to refund you your money.
Situation sucks but on a six year old boat that a company has nothing to do with it, I dont think you have a complaint.