He gets all of that correct but leaves out the important aspect of the properly fitting the prop to the shaft taper or what is referred to as "lap fitting" the prop to the shaft. Anytime a new prop is installed onto a shaft they really should be properly lap-fit together. If the prop has already been on that shaft and has previously been lap-fit then no need.
He mentions a prop being
key bound as a
number one cause of shaft failure and this is likely right up there but a sloppy fitting key, improper nut torque or a shaft that has not been properly lap-fit, and has minimal contact area, can also load the key and fracture the shaft.
Western Branch Metals, the worlds largest prop shafting manufacturer/distributor is in disagreement with that article:
Western branch Metals:
"What is the number one cause of pre-mature shaft failure?
Based on our experiences, improper propeller fit is the primary cause of pre-mature shaft failures. A properly mated propeller will reduce fatigue and avoid propeller wobble, two very key issues in ensuring smooth operation of the vessel.
Installation
The propeller should always be properly mated to the shaft taper. To insure the best fit, the taper should be coated with Prussian blue. The propeller should then be put on without the key and turned slowly by hand. If inspection of the shaft taper indicates the Prussian blue is uniformly removed then the propeller fit is good. If not, use an appropriate lapping compound and repeat the test.
Avoid key pressing against forward position of sled-runner keyway.
Do not use graphite packing in the stuffing box. Instead, use a packing material that causes the least abrasion after the lubricant wears away. Be sure to adjust the stuffing box with the clutch disengaged to avoid excessive tightness.
Align the shaft after the boat is in the water. Don't force the shaft to accommodate the engine bed, bearings, or stuffing box. Stuffing boxes should be permitted to leak slightly, thereby avoiding a stagnant water condition in the packing gland area and to avoid overheating during operation. Generally, seven drops per minute is adequate for small diameter shafts. Increased amounts are advisable for larger diameters. "
