How far does your prop slide on to the shaft?

[mnm99]

I was just installing my new props and noticed they don't slide up as far as my old ones. This may be okay, but just checking. My original ones had like 1/8" left to tighten the prop nut. The new ones have around 1/2" to go. I may be worrying, but just wanted to see what you guys have out there. I would think the most contact prop to shaft would be the best without bottoming out the nut.

 

[ttmott]

That doesn't seem to look right. The bore and shaft should look smooth and polished the full taper. Did they get fit checked with machinist dye and lapped?
And the props laying in the dirt can't be good keeping the bore clean and free of grit.

 

[Skybolt]

The inner bore of the prop looks scored and the shaft looks like it has more to go. The shaft should be "Polished" with emery cloth to knock down any burs and the prop as Tom states should be lapped. Not sure of how you got here, but I would have a shop check the taper and lap the prop to start. Hopefully you need to bring them the shaft as well.

If the prop and shaft tapper isn't perfect it can create small movement and ultimately could cause the end of the shaft to break off. Happened to a friend of mine and damaged the hull when the prop broke off, not to mention loosing the prop.

 

[dtfeld]

Also check the fit of your shaft key. Make sure it’s clean, no burrs or growth. Yours may also have a dowel pin to keep it seated, so also check that it can sit in the pin hole.

I looks like the taper is off, the aft section of the bore looks good and shiny, but no further contact. Keep applying grinding compound and forcing the prop on while spinning it. It would be easier in a machine shop, but can be accomplished in the field, with enough elbow grease.

I used this reference when I lapped mine this year.

https://marinehowto.com/lap-fitting-a-propeller/

 

[ttmott]

Also check the fit of your shaft key. Make sure it’s clean, no burrs or growth. Yours may also have a dowel pin to keep it seated, so also check that it can sit in the pin hole.

I hope he is finding all of this without the key. Get it cleaned up and fitting correctly then fit check with the key as David states.

 

[my3sons]

I agree with above. To answer your initial question, I can tell you that I have 2 sets of props that are 2 different manufacturers and they both sit on the shafts in the exact same spot. The tapers are standard and I would not expect that they should be off that much. I would investigate further before concluding that what you are seeing is ok.

 

[mrsrobinson]

I agree with all of the replies, and you said "new", are they brand new or recently tuned?

 

[Skybolt]

To take that a bit further, without the key in place. Put the original prop in place and make a pencil mark around the top where the prop and shaft meet that way when you put the new prop in place you can see where it has to meet up. Then without the key in place put the new prop in place and see how far off it is. it shouldn't be that much if there is only a little it of debris causing the displacement. As @my3sons mentioned, the tapper is a standard and all props should meet that standard.

 

[ttmott]

@dtfeld - It looks to me and with the efforts that I have done on lapping and fitting propellers, the damage to this shaft and prop may be too significant to indicate with dye or even lap out. First before the dye can be used both surfaces must be devoid of galling and scoring; you wouldn't be able to determine high/low other than maybe the small polished area in the prop. I'm not even sure that using emery cloth will clean this up. These need to be machined then dyed and lapped.

 

[Woody]

Also check the fit of your shaft key. Make sure it’s clean, no burrs or growth. Yours may also have a dowel pin to keep it seated, so also check that it can sit in the pin hole.

I looks like the taper is off, the aft section of the bore looks good and shiny, but no further contact. Keep applying grinding compound and forcing the prop on while spinning it. It would be easier in a machine shop, but can be accomplished in the field, with enough elbow grease.

I used this reference when I lapped mine this year.

https://marinehowto.com/lap-fitting-a-propeller/

I don't think the shiny section of the prop bore has been up on the shaft yet. The prop hub should overhang the end of the shaft taper so the nut can push on it, but how much should it overhang is his question. I'd think all the nut threads should all be on the shaft threads when tight. That would mean the prop hub should at least overhang the undercut between the end of the shaft taper and start of the threads. I did a google and the undercut area is 3/16" wide on a 1-1/2" shaft. But something has to be done with the shaft surface and prop bore. The way they look in the pics I think the props would end up loose with some use.

 

[mnm99]

Wow. So may responses. Guys, The shafts and props are new and am in the process of lapping them. The shaft will not be shiny where the prop slides on after lapping. I finished lapping them today and look good. The high and low spots are gone. The props were not in the dirt. They were my old props. I asked what your overlap was past the taper. From what I learned as long as 80-90% of the hub is in contact I am good at 88%. I never saw someone polish them after lapping. ttmott..Why would you say too far gone. All I did was put lapping compound on the shaft and took out the minor high and low spots.

This is from a return email from him.

Nibral material is tough and may take a lot longer lapping to get a fit you want. 80% to 90% contact is desirable.
The rule of thumb is one shaft diameter distance from bearing to major diameter of taper not to prop. Reason is long hubs will take up the whole taper length and standard tapers fall short of that.
Cheers, Keith

 

[ttmott]

Wow. So may responses. Guys, The shafts and props are new and am in the process of lapping them. The shaft will not be shiny where the prop slides on after lapping. I finished lapping them today and look good. The high and low spots are gone. The props were not in the dirt. They were my old props. I asked what your overlap was past the taper. From what I learned as long as 80-90% of the hub is in contact I am good at 88%. I never saw someone polish them after lapping. ttmott..Why would you say too far gone. All I did was put lapping compound on the shaft and took out the minor high and low spots.

This is from a return email from him.

Nibral material is tough and may take a lot longer lapping to get a fit you want. 80% to 90% contact is desirable.
The rule of thumb is one shaft diameter distance from bearing to major diameter of taper not to prop. Reason is long hubs will take up the whole taper length and standard tapers fall short of that.
Cheers, Keith

All good - no mention of any lapping being done until now and it looks like a brand new prop in the photo background. From the photos the scoring looked quite excessive, hence my concern. Lapping will remove the polished finish and create more of a dull gray but no scoring should be apparent at all. Regardless, to your original question if the hubs are the same depth on the old and new they should fit to the shaft roughly to the same point. More importantly the machinist dye indicates full contact between the prop hub and shaft and the nuts have full thread engagement and sit in full contact to the hub when installed.