Miss Geico 36 flex shaft issues

[keystoneboater]

Got my 36" Miss Geico RTR running real well, approaching 80mph stock with 2x 6s and just some prop changes. I continue to have the starboard flex shaft break when backing off the throttle. I have concentrated on prop balancing and alignment, and cleaning and greasing the tubes every 20 mins of run or so. After packing the flex shafts I usually run for a few minutes and bring it back to shore to check the temp of the stuffing tubes and they are almost always cool. I have lost three shafts and balanced sharpened props over the last few weeks - ugh. The only flex shafts I have used are the stock proboats products, any suggestions on what I should do or other flex shafts I should look into? Thanks.

[fweasel]

Where is the cable breaking? Pictures? Have you replaced the teflon liner after the cable breaks? Are you still running the original collet on the affected side?

[keystoneboater]

Where is the cable breaking? Pictures? Have you replaced the teflon liner after the cable breaks? Are you still running the original collet on the affected side?

See attached picture, it breaks right at the connection of the flex cable and the solid shaft. Haven't replaced the collet, it seams to align and connect very well. The break is 6" from the collet. I have always replaced the teflon liner after each break and clean everything well before greasing and packing the new flex shaft.

Is it because I back off the throttle too much?

[fweasel]

The transition from flex to solid propshaft is a weak point, and often where the stock cables break, however, you're exceeding even poor quality control percentages with your situation. Looking at your photo, it appears as if the cable is showing signs of unwinding, possibly due to rotation in the opposite direction. It goes without saying, you shouldn't really ever use reverse on a boat like this. You mention it happens when you let off the throttle... I'm wondering if somehow your ESC isn't calibrated properly, or there's a transmitter setup issue and reverse is being engaged, at the very least, on the right side only. That's where I would start looking. Simply slowing down, even if the prop goes full stop, shouldn't introduce loads large enough to unwind and break a cable at that weak point. Based on your temp readings of the stuffing tube while looking for signs of overheating, the stuffing tube probably isn't the source of friction. Many times from the factory, people have had tubes with too severe of a bend which pinched the flex and caused massive amounts of heat. The teflon liner would melt, the plastic tube supports would melt, the tube would spin, and the cable would show signs of heat or fail all together. I see none of that in your picture, just the break and suspicious unwinding.

[keystoneboater]

The transition from flex to solid propshaft is a weak point, and often where the stock cables break, however, you're exceeding even poor quality control percentages with your situation. Looking at your photo, it appears as if the cable is showing signs of unwinding, possibly due to rotation in the opposite direction. It goes without saying, you shouldn't really ever use reverse on a boat like this. You mention it happens when you let off the throttle... I'm wondering if somehow your ESC isn't calibrated properly, or there's a transmitter setup issue and reverse is being engaged, at the very least, on the right side only. That's where I would start looking. Simply slowing down, even if the prop goes full stop, shouldn't introduce loads large enough to unwind and break a cable at that weak point. Based on your temp readings of the stuffing tube while looking for signs of overheating, the stuffing tube probably isn't the source of friction. Many times from the factory, people have had tubes with too severe of a bend which pinched the flex and caused massive amounts of heat. The teflon liner would melt, the plastic tube supports would melt, the tube would spin, and the cable would show signs of heat or fail all together. I see none of that in your picture, just the break and suspicious unwinding.

Thanks. I know I haven't used reverse, and it seams to slow naturally not abruptly like you would expect if the ESC went into reverse. How would I check the transmitter or ESC's calibration? Transmitter is a Spektrum DX2E and the ESC is a Dynamite 120A BL ESC 2-6s. Thanks.

[fweasel]

I would re-do the ESC/Throttle calibration procedure outlined in the manual. How much trim angle do you have in the struts... are they setup as outline in the manual? Too sharp of a bend in the transition between the strut and end of the stuffing tube could potentially cause stress at the brazed joint of the flex cable. Also, you mentioned this was the right side cable, so I assume that prop spins counter clockwise when viewed from behind the boat and that the left side spins clockwise. One possible scenario is that the cables are spinning in the wrong direction, but the props had been switched and are spinning the correct way.

[keystoneboater]

Thanks,
Some great suggestions. I checked the flex shafts for proper rotation per this link:

https://forums.offshoreelectrics.com...ht=#post751990

Shafts were correct.

I then adjusted the trim on the throttle so that it was hard to put in reverse, seamed to help. I noticed when I got far out from my dock it would loose connection to the radio and stop. The only way it would stop I am thinking is if the failsafe mode on the transmitter has full break like you would have on a car. Also could be why the cable was stressed so bad and breaking since I had this happen several times. I cleared and binded the transmitter and receiver with no gas in the failsafe mode, lost connection with the transmitter again, but boat didn't stop it just slowed down. Looks like I got it fixed. The transmitter came from the factory with full break in the failsafe mode I am thinking, now it is in neutral.

Thanks!! You really gave me several things to look into. Let's hope this puts my mystery to bed!!!

[keystoneboater]

Awesome help fweasel.

Ran it again today after I got my new props (which was dropped in lake) and got close to 80 again easily, ran through two 6s packs and NO.... problems. It was clearly the failsafe settings of my transmitter.

Great help.