Have you tried emailing? I've found sometimes you can have more success and better results that way (especially if you go higher up the chain). I would write a kind but firm email telling your story.
Recipients should include your sales contact (whoever sold you the boat) and the service manager. If you still don't get a reply within a day, reply back to the same email this time with the General manager of the marina on CC.
If you spent as much $$ as you did on a boat they should make it a priority to help you.
They don't give you personal emails on the GH website but they give you a list of all the staff members and their roles within the marina and you can probably guess from there.
It's either :
firstname@goodhueandhawkins.com
firstname.lastname@goodhueandhawkins.com