Tighting the nut on a prop

[The Garfish]

Originally Posted by two stroke mick

I dont understand most of what was said.

inn dat caise yoov gottt de rite naim forr yoor bote ekseptin ittts speld lyke dis.......clooliss

gaRf

[two stroke mick]

It must be very easy to be smart when you are at this boating stuff for several years. Some day if I am lucky I too may be as smart as Garfish,

TSM

[The Garfish]

Originally Posted by two stroke mick

Some day if I am lucky I too may be as smart as Garfish

vishus butt fare

i mett a irysh sivil enjineer wunce. hee nokt mi dore an sed topp ov de mawnin too yer sorr, pleeze maiy i digg a fkin ole inn yorr dryve too mennd a browkin worter pype

gaRF

[9D280]

Originally Posted by jwalker

So you don't reckon a loose prop will be subject to various driving and water induced loads which will cause fretting of the spline surfaces and the seating taper and any knocking or impact load caused by the moving propeller will bear on the bearings and their seatings within the gearcase causing consequent wear and out of balance forces?

No, I didn't say that, what I said was

Originally Posted by 9d280

the nut plays absolutely no part in transmitting the forward thrust, and the splines take care of the rotation and concentricity of the prop relative to the shaft.

I use my current museum as an example. As I said, when I bought it, there was 1/8" axial play of the prop on the shaft because of a homemade washer behind the nut. The prop was also well mangled at the blade tips, making the vibration and off balance force situation a lot worse. How long it had been running like that I don't know, but the evidence speaks for itself: Splines on both the prop and the shaft were unmarked, which I thought was remarkable considering the state of the blades. (and I can assure you I checked before I fitted the new Prop /washer etc.) Plenty of bruising on the back of the hub as it had slid back and impacted the homemade (too small diameter as well as way too thin) washer instead of being held axially as designed.


I have never advovcated the use of a "loose" prop. I merely used the example of what I found on my current engine to illustrate a point. If your Prop is "rattling" on the splines before you tighten the nut then you probably have bigger concerns than the tightness of the nut.

[Rigaud]

Originally Posted by 9D280

No, I didn't say that, what I said was



I use my current museum as an example. As I said, when I bought it, there was 1/8" axial play of the prop on the shaft because of a homemade washer behind the nut. The prop was also well mangled at the blade tips, making the vibration and off balance force situation a lot worse. How long it had been running like that I don't know, but the evidence speaks for itself: Splines on both the prop and the shaft were unmarked, which I thought was remarkable considering the state of the blades. (and I can assure you I checked before I fitted the new Prop /washer etc.) Plenty of bruising on the back of the hub as it had slid back and impacted the homemade (too small diameter as well as way too thin) washer instead of being held axially as designed.


I have never advovcated the use of a "loose" prop. I merely used the example of what I found on my current engine to illustrate a point. If your Prop is "rattling" on the splines before you tighten the nut then you probably have bigger concerns than the tightness of the nut.

Makes sense to me, not a rocket where launching here. I just did 12hrs total run time this Sat. & Sun. with twin 460's rated at 500hp each and the props where not installed with any torq specs. Inspected the mechanics of the boat last night and props are still set 100% with no loose what so ever. Been doing it this way all my life with zero faillure.

[jwalker]

Just to put things in perspective - an indication of the forces on the drive shaft of a 200hp engine. Courtesy of TD. and Boatmad.