Paints, Topcoats, Above/Below Waterline, Fiberglass/Aluminum

[ChrisN67]

Hello Folks and happy New Year. I have had the pleasure of falling into working on three separate boats. All powerboats over 30'. One of the most significant common issues between them all seems to be the finish.

I was going with Awlgrip/Awlcraft on all surfaces with the exception of the below the waterline aluminum running gear.

For the deck I was using a the F-line Awlcraft Acrylic Urethane as due to the high detail and horizontal surfaces when combined with CraterX you can buff out imperfections easily. On the hullsides above the Waterline I used G-Line Awlgrip Polyester Urethane that is much most durable but not buffable.

The kicker is painting aluminum...I have a cast aluminum surface drive that I have been trying to determine the best paint system. I would like it to be a gloss finish such as on a new outboard. I have looked at several options to include soft anodizing / zinc rich chromate primer / epoxy topcoat or alodine conversion coating / zinc rich chromate primer / epoxy top coat. Unfortunately I have been advised that you cannot alodine or soft anodize cast aluminum...so back to the drawing board. I have access to sandblasting equipment and I am trying to determine the most resilient finish for cast aluminum below the water line.

I ordered a milspec solution:
P23377 Strontium Chromate Epoxy Primer
PRF 85285 Mil Spec Black Top Coat

I think I am going to use it but I am trying to determine the best pre-primer treatment. I am not sure why alodine conversion is not acceptable for cast aluminum.

(Q1?) Any ideas for a paint schedule for raw cast aluminum below the waterline. The boat will be on a hydro lift and the other on a trailer so I would like something with a gloss finish.

(Q2?) If you did not want to use an ablative antifoul, anyone know of a system that I can get a smooth finish for Below the Waterline similar to the original gelcoat but with osmotic protection? The longest the boat will be in the water is a three month period this summer. But when it comes back from the med it will be back on the hydro lift for the duration. I do not mind getting under the boat every 3-4 days for 30-40 minutes to clean it off.

(Q3?) Anyone have experience with cosmetic carbon fiber layup for a transom? I was thinking of vacuum bagging onto FRP then bagging the frp to the transom. Overcoat with Awlgrip clear for UV protection. I had people warm me against using carbon fiber as any transom thu-hulls will be essentially grounded to each other and there may be some sort of galvanic reaction.... Input appreciated.

Happy New Year

[Landlubber]

Contact Altex Devoe or Devoe coatings in New Zealand.

They are very experienced in protective coatings and would be happy to assist.