Do i have a case? Went in half on a boat but have no proof except about 10 family members who knows i paid half on the boat

If you can prove that you are a half-owner of the boat, you have a case, but without any documentation (and presumably title and other documents showing another party owning the entire boat), there is no guarantee that the Judge or jury will believe you rather than the other party.  You say that about 10 family members know that you paid half, but you don't say how they know.  If they have personal knowledge (i.e. not based on what they were told), or if the other party admitted it to them, there testimony can help (they will have to go to court), but if they only know what you told them, their testimony would probably be inadmissible hearsay.