Question for GN7

[gn7]

the wear patterns in the bushing are reasonably even front to back, with slightly more wear towards the back at the top. Most of the wear is between 11:00 and 2:00. We, as well as most people run 2 bushings. It the rear was the only one that wore, we wouldn't bother with the front piece.

Shafts break where they do because of the key slot. They always break right at the back of the prop, and the end of the key slot. The key slot creates a stress riser, any slot milled into a shaft. Thank goodness, because if it didn't, then the shaft would and could break anywhere along its length, and you can imagine the disaster that could create.
the LIFT of the prop on the shaft isn't what breaks them, its the torsional twist, not different than when a crank snout breaks. Which BTW, also ALWAYS break at the end of the key slot, and very seldom at the front crank throw arm, which is the next most likely spot.

Input and output shafts on the V drive, same thing, always at the end of the key slot. Occasionally END of the gear splines.

Broken a couple output shafts on desert M/Cs as well. Splines and key slot are the bane of all power shafts.

Every crank snout I have ever seen snap, broke behind the t gear at the end of the key slot. All the power is transmitted thru the damper, and there is no mechanical connection between the damper and T gear, yet never once seen a snout snap between the 2 in the middle of the key slot. The front crank throw arm sees every HP being passed thru the crank, as opposed to the rear crank arm the see near nothing. (opposite a car engine). The front arm is the second most likely place to break the crank. But never in the middle of the snout.
Just like the prop shaft breaking behind the strut, this is not caused by up forces, or some directional thrust, its 100% due to torsional twist.