Okay I’m going to throw something out that most, if not all, is going to call total BS on and I don’t blame you. But years ago both as a shipyard worker and later a surveyor I worked on the purse seiner fleet in San Pedro. Almost without exception both the Italian and Slav seiner owners would show up before launching and liberally coat their screws and tail shafts with Andy Grantelli’s STP. In fact the yards stocked this stuff in pop top cans. These guys fished Mexican warm waters and swore it kept hard growth off. Did it work well hard to say but you couldn’t convince them otherwise
Rick