Do yourself a favor and invest in a couple of box end wrenches to eliminate rounding those nuts off. Because it is necessary to tighten these things so tight, an adjustable wrench could slip and round off the points on the prop nut. There are only a couple of sizes, maybe three or so, in the size you will be needing for awhile10mm, 5/16, 12mm maybe. Stores sell pretty decent wrenches fairly reasonably now.