Why would a propeller fall off an outboard motor if nothing was hit and the water was not shallow?

Question

I rented a boat and the bolt holding the propeller onto the outboard motor slid out and the prop almost fell off. I hadn't hit anything, there was no damage at all to the propeller and I wasn't in shallow water. Outside of a bolt left loose, is there anything else that could cause this? Just wondering if it could have been the boat company trying to cause a situation that would allow them to keep my $200 deposit on the propeller.

Answer 1

Without a loose "bolt" or nut falling off, and not hitting anything, that doesn't leave many options.  The only other option would be that someone before you hit something and twisted the shaft severely.  Then it could have broken and fallen off.  The chances of that happening are very slim.  If that were the case, and it still functioned at all, you would have felt a horrible vibration and it would not have run right.  Normally, though, damage like that would destroy the lower unit gears before it twisted the shaft.  

If all it did was ALMOST fall off, and all the parts were there and not damaged, they should not be charging you $200.  It doesn't take anything to tighten the bolt back on.  If you didn't see it happen, you may be the victim of a fraud.  I would really check it out thoroughly.  Maybe even pay a boat mechanic to check it out instead of letting them do the work and charging you.

Answer 2

The propeller is held on with a nut and bolt, but the bolt has a hole thru it where there is suppose to be a cotter pin, thats what holds the nut in place.  So maybe someone was pulling a fast one by not placing the cotter  pin in so the nut would vibrate off then taking your money!  How sad.

Answer 3

Some props are bonded or force fitted to their hubs,they let go by themselves sometimes. It doesn't sound as if you are at fault. Usually the only way a bolt will work loose is if it wasn't put on properly. Hope this helps.

Max

Answer 4

definitely sounds fishy, the prop has a castle nut holding it in place,  and a cotter pin fits through one of the castle valleys. If properly done, it cant come off through vibrations. I would say most likely someone forgot to install the cotter pin, but I doubt it was intentional.

Answer 5

The propeller securing bolt should be locked in position by either a stainless steel pin or locking plate which is renewed every time the prop is taken of the shaft.

This defect was caused by the company's BAD engineering  procedures you should not have to pay them the deposit, propellers do not just fall off, allot of research goes into these engine designs but its only effective if the engineer knows what the h**l hes doing !!

Don't let this company just take your money !

Answer 6

First of all, was the shear pin intact ?. if the correct retaining bolt was used, the bolt correctly torqued, then theoretically as long as nothing was hit the prop should not have come off.

Usually the main reason for loosing a prop is if you hit something and break the shear pin then that could cause the lock bolt to come loose.

there is always the possibility the lock s***w has not  has not been tensioned correctly.