When Johnson stopped using the double prop nut arrangement and went to a shear pin, the size they choose was 9/64″. I haven’t been able to find 9/64″ rod to make replacements so I enlarge the hole to 5/32″. I find getting the hole opened another 64th of an inch to be a real challenge. To drill a hole in one of those prop shafts, and get it centered, is  way above my skill level.  When these aluminum tanks sit for decades with an open gas cap vent and/or open fuel petcock, moisture is aloud to get in the tank. Corrosion occurs in the tank and in the joint where the tank halves are joined together. I have a early Johnson tank with the same issue. I don’t know how many other potential places there might be where it could spring a leak so I’m going to put a tank sealer in this one. I keep the gas shut off, and the tank vent closed, when a motor in not in use. On the Johnson caps I put a piece of tape over the vent hole.