Prop nut torque

[fairdeal]

visiting my BIL with his Honda BF130s - was looking at the Honda Service Manual
the design of the prop / shaft / thrust washer etc.
seems identical to the a conventional Yamaha

I like the torque "range" given -
since - IMO - so long as there is "zero end play" the torque doesn't matter

[boscoe99]

Well, I am not so sure about that. Seen way too many Yamaha thrust washer failures due to insufficient torque being applied to the nut. Never heard of a failure from too much (within reason) torque.

Strange IMO that Honda can be so light on torque whereas Mercury Marine can be high on torque. I recall some of their motors specifying 100 pound feet.

[boscoe99]

Oh, if I had a Honda I would stay within the torque limit but I would be at 32 pound-feet.

That is one hellava range. I find it hard to even torque to 0.7 pound-feet. Like measuring to 0.0045 ohms.

[cleddau1]

Agree, 1 Newton is hand (or possibly finger) tight......

[99yam40]

A few years ago I saw a Merc powered boat ease up to boat ramp using a *****ing motor.
I asked what happened.
He said he lost his prop.
when he pulled it out on trailer there was no prop or prop shaft

I do not think prop nut torque had anything to do with it

[robert graham]

I've always used " good and darn tight" for prop nuts....never a problem....it ain't brain surgery,

[boscoe99]

I think it is more important on high speed high powered bass boats than it is on the rest of the stuff.

My Mercury 25 HP two stroke came with a plastic propeller nut. With no lock device. Never had nary a problem.

VZ250 HPDI's and VF250 SHO's can be rough on propellers and gear cases. Insufficient torque allows the propeller to get some slop in it. It then walks its way forward until the front of the $700 plus propeller hub starts to eat into the back of a $4000 plus gear case.

Failure to sufficiently tighten a propeller nut is not a warrantable defect.

[zenoahphobic]

Agree, 1 Newton is hand (or possibly finger) tight......

No, unless you are 10ft tall and 500 lb muscle it is more than finger tight.

[panasonic]

No, unless you are 10ft tall and 500 lb muscle it is more than finger tight.

1 N-m is only 8.8 in-lb. (lb-in for Boscoe)

On a big prop nut that your fingers can get good purchase on....that is hand/finger tight.

[boscoe99]

1 N-m is only 8.8 in-lb. (lb-in for Boscoe)

On a big prop nut that your fingers can get good purchase on....that is hand/finger tight.

lb-in for most of the world. Folks apparently confuse torque values for part of the HP calculation.

[zenoahphobic]

Whatever the way you describe it, that's equivalent to holding one pound on a ruler 8.8 inches away between your figures. I can't hold that, but then again arthritis pain might be restricting my ability to twist with my fingers!
Torque is measured from the centre of the shaft, yes a good grip with your hand on a big diameter object, using your arms, your whole body, I can achieve many many newtons and I guess you could call that hand tight. Where you would do this is perhaps on a spin on oil filter.

[cleddau1]

1 Newton is 0.7 foot pounds so with a spanner or bar one foot long a weight of just 0.7 lb hung on the end is all that is needed. If I grip the nut between index finger and thumb the distance from nut to wrist is about a third of a foot so I need to apply 3 times the weight, that is 2.1lb, about the same as a bag of sugar. Might hurt my finger a bit though....
The point I was making, or trying to, was that is, er, not very tight and you are almost relying on the split pin to retain the prop.....

[zenoahphobic]

1 Newton is 0.7 foot pounds so with a spanner or bar one foot long a weight of just 0.7 lb hung on the end is all that is needed. If I grip the nut between index finger and thumb the distance from nut to wrist is about a third of a foot so I need to apply 3 times the weight, that is 2.1lb, about the same as a bag of sugar. Might hurt my finger a bit though....
The point I was making, or trying to, was that is, er, not very tight and you are almost relying on the split pin to retain the prop.....

Agreed hard to find anything rated below 10 newton meters anywhere anyway.
I guess Hondas logic is that 1 N was good enough to stop anything rattling, that is they have no concern about the prop pushing harder than this compressing anything that can create a "hammering" damaging anything, unlike other manufacturers perhaps.

[rodbolt17]

depends on the hub design on torque and intravel of checking the torque.even if you leave the nut off,or forget the pin, you wont damage the case or shaft. you may lose a relatively expensive wheel.

[zenoahphobic]

depends on the hub design on torque and intravel of checking the torque.even if you leave the nut off,or forget the pin, you wont damage the case or shaft. you may lose a relatively expensive wheel.

Yes only a problem if you throttle back. I had the old straight 6 Mercury, put on a brand new prop, things went great for sometime, top speed good. I slowed down to test the hole shot again and the engine began to screem, the boat going nowhere. My heart sank thinking I had smashed the lower unit, upon tilting up the lower leg looked fine but just had the bare prop shaft protruding!
I believed the setup with the bended down tabs was poor protection to keep the nut on, a split pin would have done its job. What happened is speculation but the nut obviously spun off.