Prop removal

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Beekeepergreg

Beekeepergreg

Senior Member
Joined
Nov 28, 2017
Messages
150
Location
United States
Vessel Name
Mayrose
Vessel Make
Mainship 34 pilot
I have a right hand prop on a MS 34 Pilot.
Does anyone know what threads are on the shaft?
Can't see any part of the threads.
Greg
 
Not sure I have ever seen anything but standard threads on standard inboard boat prop shafts.

Clockwise to tighten.
 
Clockwise to tighten.
Click to expand...

There you go getting all technical....
Everybody knows it's "Righty tighty, lefty loosey"
 
Are you asking pitch or direction?
 
I believe his boat would have a right pitch and should be standard right hand threads as well.
 
psneeld said:
Not sure I have ever seen anything but standard threads on standard inboard boat prop shafts.

Clockwise to tighten.
Click to expand...


Don't bet on it.
It may be in most cases but you would be wrong if you were looking at my boat.
That's what I thought too but I found out my idea was backwards to what I have.
 
C lectric said:
Don't bet on it.
It may be in most cases but you would be wrong if you were looking at my boat.
That's what I thought too but I found out my idea was backwards to what I have.
Click to expand...

That's why I said "not sure".... as I lost count of removed props and shafts probably 20 years ago. :D

There's always exceptions and I figured that...but on standard inboard shafts... to me pretty rare for under 60 footers (my bread & butter).

On little props and specialty ones...particularly some outboards...where the prop just screws on... I believe they are quite often either way
 
Our last boat had one shaft with right hand threads and one with left hand threads.
 
Our North Pacific 45 has a left hand thread.

Rob
 
Got me thinking, and I'll have to check, but I would have assumed that, by design, the thread would be such that in normal operation (forward motion) the forces would always tighten the prop on the shaft. In a standard twin with counter rotation one would be right hand and one left hand thread. Seems odd to design it such that the forces on the prop act to loosen it.
 
Hopefully Northern Spy might comment with his engineering and practical wisdom and tell me why my reading and experience was incomplete enough, but it seems for boat props and shafts having and opposite thread to main rotation is no longer thought necessary if the rest of the engineering is proper.
 
I made that assumption of good machining practices with regards to rotation. Thus creating this post.
Going on line it seems more treads are just right handed, independent of prop rotation.
Maybe practical experience shows less problems when removing, when most people would naturally loosen a right handed thread. Or just stock one stock shaft....right handed threads.
 
right rotation right hand threads

on my bicycle, and probably on yours too, the right pedal (looking forward from the seated position) has right hand threads
and the left pedal has left hand threads so they tighten the pedal threads with normal foward pedaling.
but that would be the opposite situation with right hand threads on a right rotation propeller as seen from the stern. so the normal rotation would tend to loosen the prop nut ...I think

interesting observation. thanks
 
I just took the props off my MS Pilot 34 this summer and they are right hand standard threads.
 
Actually, on a bicycle the left side pedal is right-hand threaded and the right pedal is left hand threaded.

On my single-screw, right-hand rotation prop (1969 Chris-Craft) the prop nuts are right-hand threaded.

For my money, the best answer on this thread is the one prior to this, which is from the same boat as yours, since apparently different manufacturers do it differently.
 
Beekeepergreg said:
I have a right hand prop on a MS 34 Pilot.
Does anyone know what threads are on the shaft?
Can't see any part of the threads.
Greg
Click to expand...

I just removed the wheel on my Taiwan built 1987 Newburyport 37. 2 inch shaft, right-hand wheel, LEFT HAND THREADS
 
Reminds me of my old Chrysler, left side both axle nuts were left hand tread. My twin Yamaha has counter rotating props but are right hand.

Good luck
 
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