Aeromarine collet style coupler. brass insert keeps breaking

[wicked1]

you could see the drive dog move closer to the strut at full throttle and drop back when you let off. The stock 4 mm set up had a teflon spacer with no gap. I am thinking thats why the stock 4 mm cable failed in the first place. But i am new to this ,so it's learn as i go

[tlandauer]

I see why you were able to observe this phenomenon----you bench tested. Just a gentle reminder, no load, bench testing is not a good idea for the drive line and particularly on the motor. We usually just give the throttle a blip to confirm the correct rotation.
The fact that you were able to see the shrinkage with no load-----the cable will shrink when there is a load, without a load it is very hard for my feeble brain to imagine how this can take place and at such obvious amount.
Since you have been running with very little gap , I would check the motor bearings for abnormal wear. See if you can physically pull and push the collet back and forth. I think part of the reason that you were able to observe the drive dog move forward that much w/o a load is that there is excessive movement on the motor shaft and the wind that is generated by the prop is pushing the cable forward.
Sorry, I am not trying to give you a hard time, this is for me more than it is for you, I need to have a clear grasp on this subject matter for my own curiosity.

[kevinpratt823]

I would check the motor play as Tim suggested, it is also possible that the flex is stretched and worn, I would think about replacing it. I don't think an unloaded shaft should have that much shrinkage. Also, like Tim said, wide open on the bench is not a good idea for the equipment, it is also a bit dangerous. People have had the prop Break and throw a blade due to the extreme rpm and vibration.

When I wanted to see the shrinkage phenomenon, I held the collet with a wrench, then wrapped a rag around the prop and twisted it with my hand in the direction opposite it's normal rotation just to simulate a load.

[wicked1]

I am using a 1 piece cable now, the stock cable was 2 piece with square endend. There is some play in and out on motor shaft but not any up and down

[kevinpratt823]

I am using a 1 piece cable now, the stock cable was 2 piece with square endend. There is some play in and out on motor shaft but not any up and down

How much play on the motor? More than .5mm?

[wicked1]

It's about 4mm of play , maybe a hair less

[kevinpratt823]

It's about 4mm of play , maybe a hair less

Are you saying that the shaft of the motor moves in and out 4mm? If so then you have some issues, and at the very least you need to replace the motor bearings. You shouldn't have much more than just a tick of play, like half of a mm or so.
What motor is in this?

[tlandauer]

It's about 4mm of play , maybe a hair less

That's a lot, assuming that you are indeed saying that the motor shaft can move in and out by this amount. As Kevin pointed out that the movement should not really be more than .5mm, 1mm for poor production variance, IMO...
Something is not quite right, your bearings may not allow you to move it up and down, but there are spacers inside that may be wornout or missing thus allowing the rotor to move in such a way.
BTW, the factory or whoever sold you the boat was CORRECT: for a two-piece cable, there is no gap needed at the drive dog, a white nylon thrust washer is all it needs. The shrinkage of the cable is possible because of the square end that is not connected with the stub shaft.

[wicked1]

well i took apart driveline from the motor to the prop apart and put it back to together,double checked everything using your tips. took the boat to the lake and it ran perfect. as far as the motor i still have 1. mm of play in and out not 4mm like i posted.I do plan on upgrading my motor in the next few weeks, i don,t think the sss 3674 motor can handle 5s lipos to well.

thanks for your help, it made a big difference

[kevinpratt823]

Glad to hear man!