I ordered zinc #cmpnzd based on the 1.25" dia prop shaft that this PS32PH uses. I'm also missing the bolt that holds the anode to the prop nut and it appears to be a 5/16 x 18? We are in fresh water and not nearly the concern like the saltys have, but it will protect the brass prop from electrolitic corrosion. I took off the godgeon today and have the rudder supported by a floor jack. I'm going to wire wheel all of the undercoating off of it from the po, grease it up and reinstall it. After taking a mirror and looking up the rudder tube I see a cement type bedding inside of the pipe but it doesn't fill it up from side to side. I have no idea why that would be in there and as far as I can tell looks like it has something to do with the rudder sticking to it and not with sealing off the tube from water, which it wouldn't be able to do the way that it is. That tube has got to be drilled in numerous spots with some sort of a steel reinforcement going into the rudder and perpendicular to the tube, right? The rudder pipe or tube sticks about 1.125" out of the bottom of the rudder and the receiving gudgeon brass bushing is approx 1.375 deep. Both the pipe inside of the rudder and the bushing have seats that are the main contact point. No wear noticed after polishing and of the surfaces. The bushing in the gudgeon has about a .25" hole in the bottom of it, a little small for zebra musscels, I hope. Next year I'm going to shove grease into that bushing hole and call it good. It appears that the gudgeon, bolts and nuts were well sealed from water and I plan to reseal them at least as good.