1/4" flex shaft breaking

[Gapilot]

I keep breaking my flex shaft. I'm running a leopard 5692 730kv 10s in a 53" MHZ cat. I lube the shaft after every 2 runs. Any idea what may be happening? First one broke on first run after about 5'. Broke today while running straight at full throttle. Maybe 10 runs total. Lake is clear and no underwater stuff to hit. Lost prop today. Running a 2 blade 52mm.

Thanks

[Boaterguy]

that's a big shaft to be breaking.
how much bend do you have in the cable? what tubing are you running and what size is it?

[keithbradley]

I keep breaking my flex shaft. I'm running a leopard 5692 730kv 10s in a 53" MHZ cat. I lube the shaft after every 2 runs. Any idea what may be happening? First one broke on first run after about 5'. Broke today while running straight at full throttle. Maybe 10 runs total. Lake is clear and no underwater stuff to hit. Lost prop today. Running a 2 blade 52mm.

Thanks

A couple things to check for:

- Worn strut or ecsessive gap between strut and stuffing tube
- Turning the cable backwards (cables can be wound left or right)
- Poor adhering of shaft to cable

[Gapilot]

Bend is not excessive. Shaft is 26" long. Brass tubing has Teflon liner in it and seams to be a fairly tight fit, not much bigger than the flex shaft. Cable is turning the correct way. What's the best way to know if the strut is worn?

[Alexgar]

where is it breaking exactly?

[Gapilot]

Where the flex part of the cable starts.

[Alexgar]

try posting some pis of your stuffing tubeinside and outside of your boat

[keithbradley]

Bend is not excessive. Shaft is 26" long. Brass tubing has Teflon liner in it and seams to be a fairly tight fit, not much bigger than the flex shaft. Cable is turning the correct way. What's the best way to know if the strut is worn?

If it's tapered and larger at the flex entry point, it's time to replace it.
As Alex mentioned, pics would be helpful.

[Rumdog]

Teflon is a no-no with .250" cable.
Is there a gap between your drive dog and strut?

[Gapilot]

No gap. Trying to upload photo. Not having much luck

[Alexgar]

I'd probably have a 3/16ths gap between the drive dog and strut ask you and power the flex shrinks and is pulling on that cable

[Rumdog]

You NEED a gap. The cable winds when under load. When it winds, the cable will shorten. With no gap, you're giving it no room to shrink, and when it tries to..... snap. 3/16" to 1/4" depending on the cables length.

[Gapilot]

I'd probably have a 3/16ths gap between the drive dog and strut ask you and power the flex shrinks and is pulling on that cable

The first one broke and there was a gap so I made this one fit flush, but what you said does make sense. think I got the pics to work. Not sure if these are the pics that you were asking about.
Thanks for the help guys.

[Gapilot]

The gap makes sense. I'll make sure there is a gap from now on.

[Boaterguy]

the rule is generally the width of the cable, for shorter cables, a shorter gap and vice versa.
that bend looks pretty reasonable.