See if my own boat cover has some kind of legal cover on it ( sometimes an option, sometimes just included ) - speak to them and explain / get advice .
You may have the same kind of 'helpline' through your household insurance or if you have insurance through work - an employee assitance programme - will also have this.
Ask the guys to put in writing the cause of the damage and that they have not touched the timing in any way . Not sure how timing will bugger the bore ?
Ask them for thier liability insurance details as you are looking to make a claim from that .
See what responses you get on the above and post again ...or start talking to a solicitor ...