Propeller installation Does it look right?

[SailtheWind]

I just had the cutlass bearing replaced and the PSS dripless serviced. To perform the work the prop and the shaft was removed. Now that everything is back together I see the key is protruding. I had never noticed that before. The yard manager tells me this is good like that. Do you agree? Should the key stick out that much or should it be flush with the prop?

[BillKny]

The position of the key really doesn’t matter. What DOES is that the prop have perfect contact with the taper of the shaft all the way round, and for its full length. The torque is actually transmitted almost entirely by the friction between the hub of the prop and the taper on the shaft.

If the prop is loose on the taper, the key will either break, and leave the prop free-spooling, or deform and jam, making the prop VERY hard to remove.

The prop should NOT bottom out on the key. If you take the key out, the prop should go just as far up on to the shaft as when the key is in place. With the key missing, the prop should fit totally snug on the shaft, no wiggles or twisting.

[deblen]

Worth a gander. Cheers/Len


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

[kenbo]

Originally Posted by BillKny

The position of the key really doesn’t matter. What DOES is that the prop have perfect contact with the taper of the shaft all the way round, and for its full length. The torque is actually transmitted almost entirely by the friction between the hub of the prop and the taper on the shaft.

If the prop is loose on the taper, the key will either break, and leave the prop free-spooling, or deform and jam, making the prop VERY hard to remove.

The prop should NOT bottom out on the key. If you take the key out, the prop should go just as far up on to the shaft as when the key is in place. With the key missing, the prop should fit totally snug on the shaft, no wiggles or twisting.

^^This But I would add that it's most likely a sloppy install where the prop keyway wasn't cleaned and when the prop was slid forward on the shaft it bound with the key and pushed it forward as well. Highly probable that the prop is riding proud on the key and not fully seated on the shaft.

[SailtheWind]

Originally Posted by BillKny

The position of the key really doesn’t matter. What DOES is that the prop have perfect contact with the taper of the shaft all the way round, and for its full length. The torque is actually transmitted almost entirely by the friction between the hub of the prop and the taper on the shaft.

If the prop is loose on the taper, the key will either break, and leave the prop free-spooling, or deform and jam, making the prop VERY hard to remove.

The prop should NOT bottom out on the key. If you take the key out, the prop should go just as far up on to the shaft as when the key is in place. With the key missing, the prop should fit totally snug on the shaft, no wiggles or twisting.

Thank you BillKny for the reply. I feel better

[kenbo]

I'm not sure he told you to feel better. He told you how to fit a prop and he also told you that the top of the prop keyway should not touch the key. From the look of things in your pic I'd say the key is touching the top of the prop's keyway. That would take all of 15 minutes to correct.

[Cheechako]

That key COULD be too far forward. It's hard to tell. They will rise up when you push the prop on and it looks a bit that way. It appears to not be good. When you rotate the prop does it rotate without a wobble... looking at a flat face like the hub face...?

Did the yard tell you to replace that prop shaft? If they didn't at least suggest you should, then you have someone that doesn't know WTH they are doing. It's badly pitted and that could indicate it's mostly corroded inside also. I have seen a shaft that was almost like a lace structure inside it was so eaten away from corrosion. It had failed. The prop also looks badly corroded, all of it indicating some electrolysis/stray current possible going on.

[SailtheWind]

Originally Posted by kenbo

I'm not sure he told you to feel better. He told you how to fit a prop and he also told you that the top of the prop keyway should not touch the key. From the look of things in your pic I'd say the key is touching the top of the prop's keyway. That would take all of 15 minutes to correct.

Thank you for the clarification. I will have the yard pull the prop and re install.

[kenbo]

Originally Posted by SailtheWind

Thank you for the clarification. I will have the yard pull the prop and re install.

And please listen to what Cheechako said about your shaft and possible electrolysis, it doesn't look good at all.

[fstbttms]

Yeah, that's a sloppy installation. The key should not ride up out of the keyway like that. As previously mentioned, it is likely the prop is not properly seated because of it.

[MicHughV]

something is weird here......the bottom of that groove in the shaft, typically has an upward curve on it's end facing the boat, caused during the machine cutting of that groove.. ie, the end of the cut, is not square cut...which means, to my eye, the actual key has ridden up that curve somehow......the actual key, typically, has a square end on both sides..
I would take the prop off, and install the key so the end of the key lays perfectly inside the shaft "cut"...and then re-install the prop.

There is an outside chance the actual key was cut with a tapered end...

the previous posts all identify the same thing I see...

take the prop off, re-seat the key, re-install prop. if the prop is difficult to slide over shaft and key, a dab of grease will help move things along...

it's possible that is not the original key....maybe the original key got lost somehow, and the yard just stuck something else in there...???

[MicHughV]

Cheechako is correct...that shaft looks heavily pitted to me.....no question.....prop must come off for a closer look...prop looks like it has also seen better days...the forward flange looks like it's been beaten on...
taken altogether.....misaligned key..pitted shaft....dubious prop condition...hmmm.....
the shaft usually can show where the zinc collar was attached...but I don't see that....possible, the shaft and prop were unprotected in the water for a long time ???lack of maintenance and zinc replacement ???

tough to assess from a single photo...but, yes, get someone knowledgeable to give this a closer look...

[Manateeman]

All of the above comments are good advice. The whole thing is one system. Prop, shaft, coupling.. .I’d pull it all out and take it all to a good shop. Everything aft of the transmission. Check the fit of the shaft into the cutlass and the engine mounts and engine alignment. Now is the time to get this done correctly.
It’s a lot less expensive now.
I’ve been on sea trials for a new boat where both props fell off and another where the shaft log spun in the hull and we almost sank.
Happy trails to you.
Captain Mark and his manatee crew.