Prop Feathering, Suggestions ?

[The Jester]

I've noticed the prop turns while the gearbox is in neutral, and the engine at tickover, i think it's called feathering, does anyone know the reason for this and can it be stopped. This is one for the lads with inboard diesel engines.

[northeast1]

Nice new bearings causing that, mine 9 years old and takes 2000rpm for that to happen pmsl

No idea but sure you wil get a load of replys.

[lingking]

whats the gearbox type chris

[The Jester]

It's a Nanni 5.250 engine, with a Technodrive TM345A gearbox, it takes SAE 20/40 oil, i'm thinking it might just be the drag caused by the oil, because you can stop the prop turning by hand..what do you think

[lingking]

i would go with oil drag,but theres one or two lads on here will know much better than me

[northeast1]

I have the same gear box in mine and it does not happen to mine, it did when the rubber engine mounts needed lowering as it was causing vibration but because your boat is so new i am a mile away from being a expert but i would say its nothing to worry about really...if thats the only thing wrong this season your doing well

[Norman]

Aye Chris sure it's no problem, as dunc says just oil drag in the gearbox as the input shaft will still be turning and the oil will be swirling when in neutral.
It shows you've got a good line up of engine to shaft with no resistance ... nee bother ..


Feathering chris is more for yachts who use a variable pitch propeller as in the blades can alter the angle of attack (pitch) in the water and feathered is when they are turned to have no resistance to the water when at standstill, much like a feather in the wind with the individual vanes all pointing downwind with least resistance. This means the prop when stationary will not cause any drag, another way to "feather" is to use folding props that the blades only come out when turning and so fold away (or feather) to cause no drag when sailing.
Another term which may apply in your case is "windmilling"
this is where the water or current drives the prop instead of the other way around. A for instance would be a boat moored in the river and held with the current/tide passing by it, when the current runs over the prop pitched blades if the gearbox is in neutral and there is no resistance then the prop will spin (with no engine movement) due to what is actually the reverse of thrust.

hope this helps

norm

[The Jester]

Thanks for that lads, and Norman thats a great bit of info there, aye if it's the only problem i have this season i'll be over the moon