Stopping prop from turning while moored.

Stopping prop turning

If you want a foolproof method with no risk of damage, get a piece of aluminium bar 80mm long about 50mm larger than diameter of the prop shaft drill a hole through the centre of the bar the same size as the shaft. drill a 12mm hole through the bar at right angles to the first hole, then split the bar lengthwise cutting at 90 degrees to the 12mm hole. Place the aluminium bar around the prop shaft and fasten it with 4 stainless heavy duty hose clips, so that the clips are clear of the 12mm holes. The bar can remain on the shaft, take a piece of 12mm wood dowel about 30cm long and push it into either of the two holes ensuring the end is touching something fairly solid. If someone should start the engine and put the boat into gear the dowel rod will break.
 
Sounds like a good use for a boa (or babyboa) strap wrench
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And when you're not using it to stop the shaft turning, you can use it to dismantle the plumbing, change a filter on the engine, or get the lid off the pickle jar!!
 
Seajet said:
If putting any sort of disabling device on the shaft, I'd strongly suggest a red ribbon or similar on the engine controls, similar to aircraft practice of 'remove before flight' tags on disarming / locking pins.

Another option might be to put the ignition key on the ribbon leading to the disabler.

Otherwise it's just a matter of time before one turns the key or presses the starter and hears a " what the **** was that ?! " expensive & inconvenient sort of noise...
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On my previous boat I used fishing line, so on the odd occasion when I forgot to remove it, it simply broke with nothing else damaged.
 
Seajet said:
Ah, but then 'them lot' will moan about the mooring grumbling & rumbling on the seabed, or the chain rattling & snatching in the bow roller...

As for drag OK I'll bite; I believe it has been proven that a stopped prop incurs less drag than a freewheeling one, which acts pretty much as if one was pulling along a full disc the size of the prop diameter; also trundling along in neutral with the prop spinning wears things out.
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The research @Wolfson does suggest, that at certain speeds, a fixed prop exerts less drag than a rotating one but equally that at lower speeds having a prop rotating causes less drag. To a considerable extent the underwater profile of the vessel also has an effect.
The pathetic attempt of the human mind to reduce everything to absolutes in totally chaotic universe is well exemplified by this argument.
I've sidestepped it by having a prop which needs to be fixed to self-feather - that indubitably produces less drag than a rotating prop.
 
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