I have a similar question. I have Petit Hydrocoat, water
based ablative antifouling that contains copper. The boat
lives in southern FL and is hauled out every summer. It had Hydrocoat on when I bought it in 2017 and looked pretty good. At each haulout (last month was the third) it has had what I would call a light coating of barnacles
and surface slime. The bottom was cleaned about every 6 weeks when it was in the water
. At each haulout I had the yard pressure wash it.
I know, I know, everyone says don't pressure wash ablative paint! But this paint doesn't seem particularly soft and the pressure washing
doesn't seem to remove much paint. I added an additional coat with a roller 2 yrs ago without sanding
(just a good cleaning) and last year just touched up areas on the leading edges where paint seemed to have worn off. So, my inclination this summer is to do the same, touch up. My question is how does one know when to do a serious sanding and re-painting? If it looks fine, should I just keep doing what I'm doing?