When using a single propeller shaft, it is common sense to use to use a prop that will keep tight when driving forward. As most screw threads on things like nuts and props are threaded to tighten when turned to the right, the left hand rotation of the shaft tends to tighten the prop up tighter and stops it from falling off. This is the main reason why most props on models turn to the Left when looking at the boat from the rear (Stern)
However the rule goes out of the window when going hard into reverse, which can undo the prop. Hence we should fit a locking nut in front of the prop and tighten this up against the prop (Not the shaft!!) It is also essential to fit a thin 'Thrust washer' between the locking nut and the outer shaft bearing so the forward motion of the shaft is borne by the the propshaft outer bearing, not the coupling or the motor itself.
This is straightforward enough until we fit a second, counter rotating shaft, whether the props are inward or outward turning, one of them will want to undo in forward motion and the other one will try to undo in reverse, so the locking nuts are essential here, and maybe a little breakable Loctite as well.
The number of times I have commiserated with a club member because he has lost his propeller, and usually an expensive one at that. When asked if he fitted a locking nut, the answer is nearly always 'No!'
An easy way to remember Port and Starboard is looking forward, Port is on the Left...4 letters in each word.... Starboard and Right do not have 4 letters, so they can't be Left........Can They?
Ron.
