prop is spinning in neutral

[ALX357]

'Put the water earmuffs on my boat's motor in the back-yard today, and ran it for about 10 minutes ... started well and ran smooth, but as usual, the prop is spinning even though it is in neutral. Not with any force, as I can grab the hub with my hand and easily stop it, but it starts spinning again when released. I am thinking this is normal, but would like confirmation and a mechanical explanation, if anyone has one.

[kziadie]

Dont have an explanation, but my Honda does it too... from the day it was brand new. Come to think about it, most small outboards I have owned over the years have done it.

Kelly

[beene]

My motorcycle does this also. Put it on the center stand, in neutral, run the engine, rear wheel starts turning but can be stopped by hand.

G

[Andy26M]

I think this effect is just because the gear oil is so thick - even though the gears are not actually engaged, there is not a lot of clearance between them and the drive gear "drags" the oil which in turn "drags" the driven gear.

I suspect the effect might go away if the gear oil was hot.

- Andy

[nchogberg]

Regardless of the reason, I hate to hear about anyone putting their hand on the prop of a running motor!

Sounds like a very dangerous thing to do.

Leave stunts like that to the Darwin award winners

Hawg

[ALX357]

Thank you for the concern, consideration for safety. Probably good advice for most people.
As for me, motor running in neutral, hand was on the hub of the prop, not the blades, boat is firmly on the trailer, not going to jump at me.
This kind of thing may scare some people, but I am a carpenter, use power tools every day, run lumber thru a table saw, my hands a few inches from the powered blade, use a skillsaw, same thing. etc.
It is hand and eye coordination. At least it is just me trusting myself. Most of us also have to trust others - drivers, which is more scary by far.
Ever have to drive on a two-lane highway at night ? Of course we all have .... Two strangers, trusting each other while passing within three feet of each other piloting lethal mass weapons going opposite ways, at a combined speed of maybe 130 mph. And the next car too, maybe for hours on end. Hope nobody sneezes.