Thanks for your answers!
I will try offering a letter - but I guess it won't work.
I forgot to say:
would haul my boat only for a survey. These marinas
(in Fort Lauderdale) are too expensive for me to stay there for working on the boat. (I guess I have to work on the boat for at least 1 month.) I found a cheaper marina in Fort Pierce where I also could work on the boat by myself. This marina won't haul the boat without insurance.
The problem with this solution: I would have to pay twice: 1. hauling for getting the survey done, 2. the marina where I would stay for one month.
Would be much better if I could get a liability insurance without a survey including the hull
maybe somebody knows an insurance company for this!