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.
