How to remove Prop?

[NormanS]

Whichever way you use to get the prop off, be sure that for your new propeller, you specify that you want two tapped holes in the aft face. That way you will never have trouble removing the new one. All you will need is a piece of metal with holes, two bits of threaded rod, and a couple of nuts. None of this hammering and banging, or trying to get puller legs to catch on the front of the boss.

 

[paddywackcocker]

I assume the adviser was the man you later paid to replace your gearbox output shaft bearings?

+1

 

[fisherman]

Never used a puller or heat, my prop is 27in, hold a dead weight (20kg railway chair in my case) against one side of the boss, hit other side smartly with a lump hammer. You will hear ding, ding ding, donk and it's off.

 

[cliff]

Sorry lads but one never pulls something off with a puller unless it is very slack. Fit the puller and wind it up as tight as you can having first slackened the retaining nut then whack the end of the puller - just a sharp whack - does not need to be hard - more a firm tap and the taper will break and the flywheel or prop or what ever will pop off the taper. I gave up using the two hammer or heat techniques having had to resort to the above method many times after the am methods failed - it is easier to use the "chap the end" method first time. - even works on hydraulic type pullers

 

[seumask]

Cliff
Thanks for that input, an elegant solution. If I understand you correct you tap the central bolt of the puller towards the prop you are trying to pull off, i.e. along the shaft towards the gear box.
Seumask

 

[vyv_cox]

All this talk of hitting things with hammers to pull a prop off is making my engineering head hurt. Hammers have their place in a tool kit but when trying to 'pull' something off then a 'puller' is the right tool for the job to avoid the risk of damage.

I fully agree with you if the hammering is in line with the shaft, see my earlier post. The method I and others advocate, where two hammers are used to 'squeeze' the taper by striking the propeller boss, is a perfectly acceptable method. No impact is transmitted anywhere that could do damage.

 

[PuffTheMagicDragon]

Another way of removing a prop is to use its own weight. No pullers are required but this can be done only when the boat is ashore and there is no skeg in the way.


Unbolt the coupling and detach it from the shaft.
Go outside and slacken the prop nut one full turn but leave it in place.
(If the shaft passes right through the nut, unwind this further until the end of the shaft is no longer exposed)
Pull the prop and the shaft out of the stern tube.
Hold the shaft vertically, prop at the bottom, some two inches off of the ground.
Let go.
The assembly will hit the ground, nut first, and the prop will unbind from the taper.

Prop off, no damage, job done.

 

[vyv_cox]

Another way of removing a prop is to use its own weight. No pullers are required but this can be done only when the boat is ashore and there is no skeg in the way.
...........
Prop off, no damage, job done.

I have to say that this depends upon the tightness with which it was tightened on to the taper. Many people, when refitting a prop, seem to think that they tighten the nut as if it was a conventional nut and bolt clamping something with parallel faces. The result is a prop driven so hard onto the shaft that almost nothing will shift it.

 

[Daydream believer]

go to a tool hire shop
get one for 4 hours hire
take a pic of job & they will pick best model & explain how to do it

 

[cliff]

Cliff
Thanks for that input, an elegant solution. If I understand you correct you tap the central bolt of the puller towards the prop you are trying to pull off, i.e. along the shaft towards the gear box.
Seumask

Correct. You will not damage any bearings unless you smack the center bolt really hard. All it takes is a short, sharp tap. I have never failed to free of flywheels, props etc with this method even when straight pulls with hydraulic pullers have failed.
Smack it too hard with too big a hammer and you do stand a chance of brinelling a bearing but you would really have to smack it hard. If you are worried disconnect the shaft and place a brace across the gearbox housing to take the bump loading off the bearing.

 

[fisherman]

Correct. You will not damage any bearings unless you smack the center bolt really hard. All it takes is a short, sharp tap. I have never failed to free of flywheels, props etc with this method even when straight pulls with hydraulic pullers have failed.
Smack it too hard with too big a hammer and you do stand a chance of brinelling a bearing but you would really have to smack it hard. If you are worried disconnect the shaft and place a brace across the gearbox housing to take the bump loading off the bearing.

All this depends on the mass, and therefore the inertia of the shaft and prop. Likely to work better on a big prop, but then shaft length comes in, a long shaft will have a bigger mass and its own inertia will be great. You are essentially trying to move the shaft through the prop while the prop stays still.
Dropping the shaft and prop on its end presents another possibility: dropping is the way you 'jump up' a piece of shaft, to increase its diameter, will it spread the taper inside the prop?

 

[PuffTheMagicDragon]

...will it spread the taper inside the prop?

Not on a 1:10 or 1:12 taper I don't think. On some very slow tapers, in the order of 1:500, like you find on hydraulically expanded boltless coupling sleeves that you sometimes find on intermediate shafts on ships...maybe. I'm thinking 'practical' and not 'theory'.

 

[seumask]

I can now report back on my prop removal.
I bought a 6 inch puller from halfords for £29 and applied this to the prop on a 2 arm setting, before compelety removing the nut. Wound up the puller by hand to reasonably tight and with two taps of the hammer on the end of the puller the prop moved off.
Now the interesting bit, the shaft turned out to be 25mm diameter tapering to 22mm over 60mm with a 10mm wide key in it 55mm long. I'm not sure how one speicfies taper is that a 1:20 or a 2.5% gradient over the 60mm.
According to the kind people at Darglow that means the shaft is " The old Volvo" Standard, and they are busy milling up a hub to fit it.
Thanks for all your kind suggestions
Seumask

 

[PuffTheMagicDragon]

That's a standard 1:10 taper. The 10mm key sounds a bit oversize; I would have expected something more like 8mm. Glad you got the prop off with no trouble. Make sure that when they broach the keyway you check the fit of the key as well as the alignment. A 'dry-run' assembly of prop and key on the shaft will show if the machining is correct: there should be no sign of wobble at all.