Years ago a few hours before departing for a trip to the Caribbean I discovered my Onan would not start . I had a mechanic come aboard and the first thing he did was to find and replace an inline fuse ,that I did not know existed. It is behind the engine on the port side close to the front . It may go to the starter . If you cannot find it let me know and I will go out to my boat and take some pictures.
Hope this helps,
Pat
SM Shenanigans