What you would find next is how do you center the point & make it all symetrical? Make a s straight edge w/ a block on 1 end, the block should Have a V cut in lengthwise that is well aligned w/ the straight edge. Clamp it to the prop shaft so that the straight edge goes forward in exact alignment w/ the prop shaft. Meaurments determined by your gearcase, it needs to be outside of the widest part [needs to be reset per side of skeg]. With this in place you can measure in anywhere to get it 'on'. By eye would work but with this your sure.