Double taper propeller shaft

[Larry aberg]

This morning I picked up 2 new 2.25 double taper shafts with new couplers for my ZF301 trans. Cummins 6CTA8.3 motors.

We are replacing bent shafts that cannot be straightened since someone used a grinder on them. The couplers are suspect looks like someone hammered on them.

Do I fit the couplers similar to a propeller, fitting the coupler without the keyway first followed by the keyway?

Topic

[Tony Athens]

Larry,

Glad it all worked out.. Good job!

Tony

[Larry aberg]

Comments after shaft replacement

We replaced shafts and props all work great. Completed 1200 mile cruise this summer north. Vibrations are all gone.

My vibration issues were not related to the old shafts but inadequate installation by the previous boatyard. After we hauled the boat we removed the prop nuts maybe 40 ft lbs of torque but they looked like they were on the shaft. The couplings nuts insude engine room were next and i was able to remove them with my finger’s no torque on them. The couplings fell off the shafts when i pulled the nut.
Needless to say i was a bit pissed at previously paying top dollar for the installation and to find this one year later.
We installed all new equipment and with the help of Tony’s article “Big nut little nut” and this Forum. The yard did frown on the installation using epoxy on the nuts as well as the big nut first! Oh well, i dont trust boatyards anyway.

[Larry aberg]

Lapped shaft

Good shaft no high spots

[Larry aberg]

Shaft high spot

Picture of lapped shaft and high spots

[Larry aberg]

Coupler fitting

I fitted the couplers lapping the coupler to the shaft.

One shaft looks great. One shaft has a couple of high spots shiny marks on the shaft picture attached.

I can feel the coupler catching on the high spot.

Do i continue lapping trying to smooth this out, try polishi it out?

[Rob Schepis]

If you do as you say with the prop be 100% sure it is blocked at the hub, not anywhere out on a blade, or you can twist the blade

[Larry aberg]

Torque values

I have read “Big Nut little Nut” half a dozen times knowing this project is coming up a good read thank you.

I can get a deep well socket on the coupler end and to conduct final torque values i should have the prop on.

Ive seen guys put a 2×4 between the blades on the prop and brace to the ground to hold the shaft while fightening the bolts on a prop.

Is this acceptable way to hold the shaft without damaging the propeller? A better way?

How many ft lbs are we looking for at the coupler nut?

In your article on prop nuts you mention several hundred ft lbs for propeller nuts. How many ft lbs for 2.25″ shaft?
The machine shop sent me bronze and stainless nuts for the prop end. Which ones would you use?

[Tony Athens]

With this style,install the hub as if you were doing a prop.. Your biggest challenge may be getting the nut tight enough.. Can you get a proper socket in there? Locking the shaft and hub while tightening? Can you be sure the nut stays TIGHT?..

Tony

[Larry aberg]

Comments

Much appreciated, i purchased shafts and couplers/hardware from marine Machine shop and they said they matched the couplers to the shaft as they machined both ends.

I just want to make sure i install the assembly correctly.

I do t trust the yard personnel as they beat up theshaft and couplers last year.

Props are 32 x 32 four blade, whats the prop puller i should be using?

Thanks again

[Larry aberg]

Shat couplers

[Larry aberg]

Picture of shaft components

[Larry aberg]

Pictures of shaftz and couplers

Pictures of shaft

[Tony Athens]

In so many words, the answer to you question would be————Yes, the same as for a prop.. But with that said, couplings on tapers at the gear end do not always follow any particular SAE spec as to how that coupler is held place.. ..Plus,many times, you need a custom socket or tool to install it properly..

If you need specific guidance, than I would need a lot more as to pictures of all, etc etc..

Tony

[Author]

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