Regarding bottom condition. I have two boats, both painted with ablative paint. I usually put on new paint each spring, one coat on the bottom and two on the sides and transom. If there are chipped or pealing spots, I give them a light sanding and spot treatment before painting the entire hull. If all thr old paint were worn away, I would apply multiple coats per the manufactures instructions.
Three or four seasons ago, I switched from Interlux CSC to Pettit Hydrocoat, mainly because I wanted to try water based paints. They are in a way trickier to apply but the lack of odor and the ability to clean up with soap and water is such a great advantage that I would not go back. You can also paint the hull and don't really have to follow a window of time to launch. They can sit painted on land for weeks or more. I could probably get a few seasons on a paint job but I do get some peeling in spots down to the original anti-fouling paint. Some high wear spots may peel also like where the trailer rollers sit.
One boat is used in salt water, and is in the water all season. The other is used in brackish water and is also in the water all season. Each boat may sit at the dock for weeks at a time.
I have not had any barnacles attach to either painted hull. I get barnacles on the motor mount area, and lower part of trim/tilt which is in the water, in some of the water pickups and on transducers (even though I use MDR transducer paint on them). I sort of use anti-fouling spray for aluminum on motor parts that get salt water but I haven't had great luck with those sprays. I get terrible results using the clear Interlux but have had better results with Alumacoat which is colored and not the Yamaha color.
I do get a lot of slime which for the most parts power washes off when the boats are hauled.
I have noticed that the Hydrocoat even though it is ablative, dose buildup over time and can get thick. It's probably time for a good sanding or blasting. Ha, I say that each fall and in the spring say " I'm not going to sand this hull"
One addition comment on Pettit Hydrocoat; One of the more important steps is to really stir the paint. I mean really stir with a drill and a paddle and for several minutes.. You have to stir it also as you use it. It settles quickly.
Last season Pettit put a new sticker on the can to advise you not to apply too thick of a coat. That recommend a roller with a 1/4 nap. Good luck finding one of those. Don't use foam rollers either.
If I weren't so anal, I would have someone else paint my hulls.
