Does anyone know of any who makes a drive dog about .75" long with two or four set screws and a .38" grove in the center. I could build a small aluminum bracket off the back of the prop strut that could catch the prop shaft if the cable weld broke.
I would think you would put a set screw in opposite sides of the drive dog to balance the shaft?
I would also think you may be better to make a single piece rather that two separate?
Open for suggestions.

Having the drivedog extended that far beyond the bushing would put quite a bit more load on it.

.75" + .250" drive dog clearance would have the prop a ways behind the support of the bearing.

Most are running welded stub cables that do not run a stationary drivedog against thrust washers so it would need a good 3/8" movement front to rear to be sure it didn't contact the retaining bracket.

Great idea and I saw a guy do almost exactly what you describe.

An oversized shaft with a deep groove and a retainer stud protruding into the groove is common way some have used.

I am reading on other sites about continuing cable breakage problems, the resulting loss of the propeller shaft & the propeller. Is there a designed system that eliminates this problem, no matter where the cable breaks?

The first photo shows a complete cable, propeller shaft, bushing, drive dog & lock nut. A soldered in place, brass sleeve (.250" ID X .2812" OD X 1.500" long), which reinforces the flex cable propeller shaft joint CANNOT PASS THROUGH the machined bushing (.250" ID X .375" OD X 1.375" long) in the event of cable breakage occurring at any point from the sleeve to the engine collet. The brass sleeve rotates freely inside the already existing stuffing tube (.2812" ID X .3125" OD X whatever length). The propeller shaft bushing is a slip fit into the strut & is held in place with a 3-48 screw. The bushing is precision machined from B-10 grade Bearium Bearing Bronze. It is unaffected by the propeller's radial load & the propeller shaft's RPM, therefore it lasts indefinitely

Another part of this system, which eliminates repeated removal of the cable to facilitate lubricating the cable, is the grease fitting & Teflon sealed rubber boot at the upper end of the double walled stuffing tube. A small grease gun & Lubriplate Special Marine Grease #2 gives a very low drag lubricating system. A small amount of grease is pumped into the stuffing tube before each run, making removal of the cable un-necessary, since the grease always moves down the stuffing tube, towards the strut!

Jim Allen