Interesting question.
I think the key is to do something that is not "work" but something you enjoy. If you are always fixing other people's boats, how likely are you to spend time fixing your own? It's the old saying, the cobbler's kids are unshod. If you went into the marine tech area are you willing to get ABYC certifications or enroll in a training program?
At one point I had a retirement plan that included working at a BoatUS store, and then WM, then WM closed its doors. So much for that plan.
Teaching sailing would be a lot less work like, might be fun, and would generate some income.
Since I retired 5 years ago, I've done a little writing and been paid for it. I also had the opportunity to return part-time to my old profession. That's worked out well, as I mostly do the parts of the job I liked and not do the parts I didn't like while setting my own hours.
Health insurance is a major concern. Fortunately, my employment contract provided for health insurance coverage from my retirement until Medicare kicked in. They also covered my wife's insurance, one of the reasons we got married before I retired.