Prop Shaft

[gn7]

Since nobody has a patent on props, if you design your own, why would you want to send someone a royalty check? As for hydros running shorter shafts that is true of the modern boats. I know the old conventional hydroplanes ran one inch shafts from the engine back to the prop, right between the driver's feet with no guard. Our 280 had a 1" shaft and every boat up to the seven liters I knew of used one inch shafts. I'm not sure what the unlimited ran back in the day, but even at 1 1/8" that is a lot of risk running between the driver's legs. I don't recall ever hearing of a shaft on one failing anywhere other than the prop or the coupler. Shaft whip wasn't the cause of failure.

Bob, how many shafts do you know of that have failed in the middle?

NONE. I said that repeatedly. It just does not happen. I seen a TFH kick both short shafts out the back on shut down when the twin props were in infancy. But that was a mechanical failure at the couplers.
Never seen a single prop shaft fail between the back of front coupler and the back of the strut..

Pat Hoban GN30 had a shaft fail dead center in the log. But it was a brand new shaft of "commercial over the counter" 316 that broke the first time out, and broke on an EXTREME angle due to a flaw in the material. Looked like the mill "spliced" the run with a high angle scarf type joint you would use joining to end grain planks. Shit material that had no business being used a boat shaft.