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[dickyp]

Further to my post regarding prop connectors, I must have misunderstood the information kindly supplied by members as for the last 2 hours my boat has been standed in the middle of the lake at my local park, much to the amusement of a couple of dozen watchers all giving advise.

What I did was

1 put the prop on the threaded shaft
2 put washer against outer tube and nut against prop
3 Slide prop shaft inside tube
4 Put washer at end of tube and put on nut
5 Put another nut on loosely
6 Connect coupler to threaded shaft and tighten loose nut against it
7 Fasten other end of coupler to motor shaft with grub screw

I don't know what caused the problem but the exposed shaft between the coupler and the outer shaft case locked up solid

Any ideas please on what I did wrong

[Shipmate60]

The shaft locking is usually caused by the inner locknut coming lose and tightening against the outer prop tube.

Bob

[malcolmfrary]

Locknuts have to lock against something, usually either another nut or other threaded device on the same shaft.  The prop locknut is wound hard against the face of the prop, the coupler locknut against the coupler.  Anything rotating should have a washer between it and a non rotating part.
From the description, there are two nuts at the coupler and.  One is locked against the coupler, and is OK.  The other is not held, so driving the boat will allow it to move.  If the rotation of the shaft allows it to tighten, it will.  Either dispense with this nut and replace it with a spacer tube to get the required lack of end play, or fit another nut to lock against this one.  And, of course, the washer. 
The washer at the prop end acts as a thrust bearing when going forward.  It also needs one at the inner end to act as a thrust bearing when reversing.

[dickyp]

I know i'm thick

I think the locknut against the coupler may have come loose because the brass insert in the prop side of the coupler had pulled out slightly

Looking from prop to motor, the motor is turning anti clockwise (to meet the prop shape); has this any effect

Would I be better using 2 lock nuts aginst the coupler and prop shaft ?

Thanks guys for your input

[Shipmate60]

2 lock nuts wont help, as long as the outer lock nut is tight against the prop and the inner lock nut tight against the coupling with washers between the rotating shaft and the outer tube it will be fine.
As to the amount of play in the inner shaft to the outer shaft.
You should just be able to feel a slight fore to aft movement (about 1/32 inch).

PS NOT thick, just inexperienced, it has happened to most if not all of us at sometime!!

Bob

[dickyp]

Thanks for your responses guys.

I thought that I had set it up as your latest post but perhaps I will have to try again although at the moment I am very wary of showing myself up again

[Shipmate60]

The dynamics of the shaft change when in the water and load applied to the shaft.
The shaft will move inward when going ahead and astern when going astern, this will put extra forces on the lock nuts.
If in doubt clean up the shaft and nuts and use loctite on the threads BUT this will make them a mare to remove without heat.
But I have to say that I havent used threadlock in any of my models.

Bob

[malcolmfrary]

If the locknut moved, it wasn't locked.  It needs a spanner on the coupler, and another on the nut.  The two are then wound into each other quite hard.  This way, both are pressing against each other and the thread.  A loose nut, when the shaft its on rotates, will do its best to not rotate (inertia).  This means it has to try to travel along the threaded shaft, which it will do until it finds something to stop it, like the inner end of the shaft outer.  It will, at that point, seize solid.

Much the same applies at the other end.  The prop has to be firmly held, and the locknut wound into it.  Holding the shaft and winding the nut into what it is needed to lock just does not work.  Many replacement propellors are sold through this not being fully understood.

[john s 2]

If using Locktite please be aware that it comes in different strengths.The one you would need is nutlock which is avaliable from good Motor Factors.Do not use studlock, bearing fit, as these will require heat to undo.John.