I've heard from power boaters that this year has been the worst for growth and are having to short haul to clean running gear much earlier than in previous years. The yard crew is saying the same, and they think it's due to warmer water temps.
If he has an ablative, and hasn't been moving the boat, he's probably gonna have an issue.
Being invloved in marine Antifouling development and testing for over thirty years i would like to dispel some myths around Ablative Antifouls.
Basically Ablative and to some extent Self polishing antifouls do not clean themselve by just moving the boat!
While boat speed will effect some growth removal most growth is removed by the lack of INITIAL attachment and inadequate "SUBSEQUENT" attachment to the ACTIVE LAYER of antifouling.
What does this mean?...
as a layman (if i can)...
An Ablative Antifoul is made using Semi soluble and soluble resins that have Cuporus Oxide ( a derivetive and more active compound of copper) blended and suspended amoungst them (along with other additives such as anti slime agents, solvents, color pigments...)
When the Antifoul (applied and cured on the hull) comes into contact with the salt water it reacts with the salt (sodium chloride. Sodium is a active metallic compound) and the initial Antifouing layer softens and slowly ablates cuporus oxide on the paint films surface.
This soft 'cuprous oxide laden film(goes green in white A/fouls) is the 'active layer that does all the work until expleted! then falls away to expose another new layer!
Growth that tries to attach to the soluble, soft Cuporus oxide laden "exposed" layer are either killed by the "biocide" (Cuporus oxide) and fall away or reach a certain size / wieght and fall away as the "soluble layer" breaks down to expose a new layer.
Moving the boat just creates a force that advances the process slightly.
Good Quality Ablative A/Fouls will never have growth on them and only slime. however if poor Mixing, application, and over zealous cleaning occurs and the product is either compromised or worn away they will have growth very quicky! (mainly on the old primer or previously spent old A/Foul)
with Ablative A/fouls they will 'clean" themselves with minimal water movement but can be expended prematurely if you either ...
go to fast!
clean to harshly
Apply to thin a coat or film build.
This info applies to salt water only. Fresh water is another problem as Copper based A/fouls do not work in fresh water as thier is no sodium chloride to "activate" them. this is another topic for another day.
I Hope this clarifies (in a crude and basic form) the workings of Ablative a/foul.
I apologise for the spelling. My spell check is broken and i had to rush this reply before going out!