Prop shaft came loose

So a new member of my ski club was telling me how he welded the shaft to the coupler on his friend's Centurion because the set screws wouldn't hold it in anymore...

Merritt - Kudos for sticking with it. You are learning a new skill set, something you can pass onto your kids.

It sounds to me like the current shaft has been beat up. The easy thing to do now is to buy a new ARE shaft. They are much easier to remove at the next 'incident'.

I live in a heavy industry town & haven't found a machine shop without a high setup fee.

Peter, I think I understand now. Can a machinist get a new coupling, bore it and refurbish the shaft for less than $400? I was resigned to just order the set from Skidm.

Merritt

Max Shaft Diameter = 1.0000 Min Coupling Bore = .9995 resultant fit .0005 tight.
Min Shaft Diameter = .99975 Max Coupling Bore = .99975 resultant fit size on size.
These are just representative numbers to get to what Pete was saying about the "shrink fit". Actual shaft diameters and bore may be different. Just trying to get you visualizing what people are saying.Its just math.

Also I agree with Glass Seeker. Nobody was trying to insult you or give you a hard time. Just slow down do some research on what these guys are saying and go from there. These guys know there stuff and their advice will help. Yeah sometimes the diagnoses isn't fun for you or the credit card but is is all worth it when you get to enjoy the boat...

no one is calling you anything, no one is trying to hurt your feelings, only attempting to get the point across, I think if you read the thread from the beginning the answers are mostly there.

yes these things do cost money but following the advise here can be much cheaper than winging it.

slow down take a breath and maybe don't ruin a new coupler, if the shaft is in fact jacked up(fretted) worn, not round, not in tolerance, and since you have not heat shrink fit it on the shaft then that says the shaft probably is bad. measure it.

Look guys, I apologize. I'm a school teacher with three kids who like to ski. I am not a mechanic. Nor do I have loads of money to spend on one.
In the past you guys have helped me replace the steering cable, fix an overheating engine, rebuild a carburetor, align a shaft prop, decide how to handle a broken fuel gauge, give suggestions on towers versus extended pylons, and how to fix several routine issues with a thirty-five year old boat; and I thank you all. Everybody usually responds in a matter of minutes instead of days and have been patient with my amateur attempts sometimes explaining things in plain language I can understand.
I usually get access to a lake house for two weeks a year and spend half the time keeping the boat running. I'm not complaining because I love getting out of the classroom and getting my hands dirty rather than just doing the easy thing of selling a classic Ski Nautique and buying some stupid plastic boat like the Seadoos and Sunbirds others buy.(I think you guys know what I mean.)
I have very limited assets and can't just shell out hundreds of dollars every time I go out on the water.
In previous years I have had plenty of help from the experts here.
I normally search every forum post first so I don't ask questions already explained elsewhere.
So, please, if you are willing to explain to me what I should do and how to do it like most of the Grand Poobahs have done in the past then I appreciate the help. I need it in simple language to a guy who has never messed with a shaft before.
However, if you feel the desire to answer with "you're just doing it wrong" or "you can lead a horse to water" or some other unhelpful condescending response then please stay out of the way and let the guys who are willing to take their valuable time and actually help me to understand do the replying.
I'm doing the best I can with what I have.
Now,
I took the coupling to a veteran boat mechanic and machinist. He told me where to go to get the right coupling. I got a coupling made for a Ski Nautique identical to the one I took off. I don't know what it means to be heat shrunk. Is a heat shrunk coupling different than the coupling I took off or is it a process for mounting the new coupling?
I want to do it right if I can.
Do I need to remove the prop and shaft completely in order to fasten it to the coupling or can the coupling be replaced without removing the shaft?
What length square rod key do I use and how do you properly seat it in the coupling and shaft simultaneously?
These are the things I need help in understanding.
Call me whatever insult you want, I guarantee it's not worse than what my elementary students have called me. But if you are the patient mentor type, willing to help a newbie amateur, then you are acting like the true professionals who have helped me in the past. Thank you. You are the men I have grown to truly respect and come to for help.

wow, post on here asking for help, get help, ignor help and do exactly what told not to do.

you can lead a horse to water...

get ready... here it comes...

It was a 1inch coupling. Shaft is not egg shaped. Flat front with keyway. Coupling has two set screws. Each 120 degrees around from keyway. Not heat fit.

New coupling same shaft. Idle speed it was smooth but when under mild speed it is pretty rough.
I didn't have my gauges with me to align it. Got the gauges from home and I will do a thorough alignment tomorrow morning; weather permitting. Anything else I need to check?

You don't actually need live approval you just aren't doing it correct.

I have pics but need a web guru to give me permission to post.

Also pictures of events like this are worth a thousand words.
If you can post some pics of the shaft and coupler it would help with the diagnosis. You maybe wasteing your time and money trying to put it back together.

Well, last time I checked the alignment I used the gauges suggested here and it was aligned perfectly. I wasn't going off of just the turning by hand.
No, I don't have the tools to measure the ID and OD of the coupling and shaft.
All the marinas were closed today but I'll have someone look at it in the morning for suggestions.