I’m not sure there’s ever a perfect time, but I think it might be the right time if you’re really questioning it. Since you haven’t done any interior designing for yachts yet, I would try reaching out to a few people who do it before you make the jump.
Maybe you can even shadow someone to see if you really like it and you’re good at it. I don’t think it would be the smartest move to jump into it if you’ve never tried it before.
If you are able to reach out to interior designers who work on yachts and even shadow one or two, and find that you’re still drawn to it, then I say go for it.