Originally Posted by syjos
I've tried a variety of prop paint and they are all mediocre in protection from growth. In the PNW, barnacles and slime are the major problems.
Prop Speed was pretty good but had to apply it more frequently. Prep and painting is a lot of steps.
Interlux Interprotect 2000 epoxy primer and Micron Extra bottom paint worked the best. Lasted 5 years, kept growth from growing on the prop. Prep and painting is a lot of steps. The bottom paint on the tips were worn away by year 5 but the center of the prop was barnacle free. Interlux recommends Trilux 33 for paint but the Extra worked fine.
Rust-Oleum Cold Galvanizing paint spray paint works pretty good. No prep other than sand. Lasts one to two years. Pettit Paint sells the cold galvanizing paint for underwater metals and calls it "Pettit Prop Coat Barnacle Barrier" and it costs about 5 times more than the Rust-Oleum. Has less zinc in it than the Rust-Oleum.
A lot depends on the water where you moor, the RPM of the prop and how often the boat is used - how often the propeller is spun. We keep the boat in the water all year. Those on the east coast, who haul out every fall has an advantage on the prop maintenance.
Sandpiper has a 2.5 to 1 gear and cruises at 1700 rpm. The propeller spins at 680 RPM. Not enough RPM's to spin the baby barnacles off the prop.
I am early in experiential application of the Petit cold galvanizing paint on my running gear.
Last year I applied Petit to all of my running gear. Going in I had barnacle growth of up to 1" tall and 1" diameter barncles on 13 months since the previous haulout, when I had painted the running gear with Petit Horizon antifouling, the same as I use on the hull. The hull had no barnacles whatsoever.
This year the barnacles were a little smaller. the propellers were completely covered with very small barnacles and the rest of the running gear with larger barnacles, though none as large as the previous year. This time I used Petit Horizon on the port side running gear and cold galvanizing on starboard. I don't have high hopes for either.
The days of no hard growth seem to be gone with the switch away from high copper content paints.