In a previous lifetime I have been through this mucho times as the owner of the repair shop... As a repair shop owner I can tell you with certainty that I HATE it when a job exceeds the estimate... I much prefer that the work finishes on time and on price... That way I have a happy customer who will come back, and I can get the next repair job started on schedule... But in the real world there are always set backs... . Last, as a former 'mechanic' let me tell the OP - you can't win by being obstinate... Pay the bill... Remove your boat... Then have an attorney review everything and if said scumbag lawyer agrees you were cheated, sue... cheers ... denny