Who to avoid at all costs? That's easy: Sean Silverman. That dude set the injection timing so far off on my engines I wound up with broken rings and had to rebuild both engines. $70k nightmare. Plus just all around weird, he and his helper would show up at like midnight and work until 4am, stuff like that. One of the worst experiences of my life.
Luis at J Diesel is awesome: (386) 864-3179. He rebuilt both engines after the nightmare I went through with Silverman, plus he is good with maintenance. Couldn't recommend highly enough.
General fix-it's, a/c, plumbing, electrical, etc.: Florida yacht support: (904) 372-3838. These guys are good, also couldn't recommend them highly enough.
Diver: DS Dive Service: (904) 755-4546. They do a great job.
I used to use Blissful Bottoms for the best part of 15 years, and towards the end I had constant problems with them not showing up. Annoyingly, they also wouldn't tell me when they skipped, so I'd be out in the boat with 15 people and the fouling was so bad the boat wouldn't plane. It gets annoying when what's supposed to be a quick run to lunch and back takes 3x longer. Back in the day Ollie used to be good, but nowadays he hires a lot of his work out and I don't think there's a ton of oversight as to whether the guys he hires do the job. Looking back at it, that had been going on for years. Since the new dive service it's like I have a whole new boat. Always planes when I want it to, it's not a crap shoot anymore, and I get 9 knots at 1200rpm instead of 1400. Stays on plane at 1900 instead of 2100. I wish I had realized I was getting ripped off years ago, I can't imagine the amount of fuel I've wasted.
The final straw was I had just paid their bill and the boat was hauled out on short notice the following week because my insurance company waited to the last minute to tell me they wouldn't renew without a survey. When it came out of the water the surveyor (Bill Gladding) called me and said you're getting ripped off by your diver and sent me pictures. The 1' of the hull right under the waterline, basically just what you could see from the surface, that and the props were the only thing they had cleaned. The rest of the hull had an crazy amount of fouling on it, months of buildup.
The marinas around here tend to suffer from the problem Ralph is describing, where all the good mechanics either retired or got poached to take jobs somewhere else. They try, but it takes them weeks to get to it, and if it's engine work half the time they'll tell you they don't have a diesel mechanic on staff anymore and to call around and find somebody yourself.