You first have to tell us if the prop is on a 'tapered' shaft or a 'straight' shaft.
• tapered shaft - the prop shaft is of noticeably larger diameter at the 'fore' end of the shaft where the prop is attached, and with a noticeably or visibly
smaller diameter where the prop nut is attached. (Most common attachment nowadays.)
• Straight shaft --- the section of the shaft diameter at the threads of 'prop nut' is only slightly
smaller than the diameter of shaft 'in front of' the propeller. (Uncommon; but not so uncommon, in 'older' boats.)
' shaft -
Get/rent/borrow a gear puller ... you'll need to match the number of 'arms' on the gear puller to the number blades on the prop.
• Back off the prop nut - just a few turns.
• Apply the gear puller with the 'arms' of puller firmly engaged with the 'front' end/surface of the props hub ... NOT on the blades! The end of the 'screw' assembly of the puller must be exactly centered on the end of the shaft. You can 'back off the nut' to help hold the screw assembly centered on the end of the shaft.
• Turn the jack screw on the 'puller' as tight as you can (by hand) .... if the prop become loosened during the tightening of the gear puller, the prop nut will stop the prop from coming off when the prop 'pops' off the tapered shaft.
• If no 'pop', then get an assistant, a large weight/mass (sledgehammer will do) and large copper
hammer. Have your assistant hold the large mass 'tight' against the shaft or strut or whatever is closest to prop; With the gear puller strained to maximum 'hand tight', give the HUB
of the prop increasingly sharp and more powerful 'WHACKS' (perpendicular to the long axis of the shaft) until the prop 'pops' off. Remove the nut, slip off the prop, preserve the shaft 'key' for when you reinstall.
( you may want to search Mainsail's Compass Marine website for honing/lapping
a prop and prop shaft) for 'best' installation for a tapered shaft.)
• Make sure the prop shaft taper and internal surfaces of the prop hub are clean and 'bright'. Use industrial fine 'crocus cloth' (an industrial fabric based
type of sand paper - from a hardware store, etc.) to polish the taper and the internal taper of the prop.
• Install the 'key' in the keyway, Apply a very
light coat of oil to the taper AND the shaft threads, Attach the prop, attach the nut. Make sure that the 'key' stays in place during this installation ...
• Measure the diameter of section of shaft that has threads
, measure to the closest 1/16"
• Get a torque wrench, a deep
socket to fit the nut ... then go to https://www.boltdepot.com/fastener-i...ed-Torque.aspx
.... match the size listed there to the measurement made for the diameter of the THREADS
, as above. These values are in 'foot-pounds' or ft.-lb. Choose the torque value based on thread diameter AND material ... if the nut
is bronze, choose bronze torque values, etc.
•Hold the prop blades to prevent rotation, and apply the proper torque ... when close to the torque value - 'whack' the hub with the bronze hammer, etc. to help 'seat' the prop to the shaft taper. Then 'back-off' the nut until loose and repeat torquing & whacking (2-3 times), apply the cotter pin. etc. You can 'back off the nut' up to one-half turn in order to fit the cotter into the castellations on the nut; but, ONLY if you properly
torqued the nut when forcing the prop onto the shaft taper.
Note - if you don't have a torque wrench, use a '6-point' 'box
' wrench for the proper size for the 'nut' AND a box wrench for the closest size of the diameter of the 'threads'. Put the 'thread sized' wrench on top of the 'nut sized' wrench ... and make a 'mark' of the length
of the thread diameter sized wrench .... Use the nut sized wrench on the nut while holding the blades ..... BUT your hand may not be on
that wrench 'above' that 'mark' ... and tighten the nut as 'reasonably
as hard as you can' with your body strength. This assumes youre not a 98 pound wussy nor a 'monster'; just don't 'over do' it.
The 'length' of wrenches are designed so that the 'average' (5'-10", 160-170 lb.) man will be applying a close approximation of proper 'hand tight' torque to NON-METRIC
bolts, etc. Don't do this if the nut and threads are 'metric' ... which are inferior to the thread strength and torque bearing ability of 'english' (Whitworth
/BSW, SAE, ANSI, etc.) bolts, etc. Sir Joseph Whitworth (1803–1887) was an absolute genius!
Get back to us if this is an old-style 'straight' bore press fit or 'interference fit'.
Hope this helps.