Prop shaft came loose

No expert but I believe that the heat shrunk coupling is a coupling for a non-tapered shaft that you must heat up before installing. I have read posts where people heat them in the oven and then install them. It may be possible to install while the shaft is in the boat but would definitely be easier with the engine removed so you can slide it in the other way. Maybe somebody else will chime in...

From experience with this issue though I would highly recommend the ARE shaft system. You will save yourself a bunch of time and hassle. Yes its expensive but that is why they call it a boat...

Break Out Another Thousand
Hole in the water that you throw money into
Etc...

Thanks guys. I will look for a new shaft/coupling set to get it right. ARE seems advised by several guys.
I also found Peter's video on shaft/strut alignment. Now THAT was helpful. I wish I had found that earlier. I was trying to figure how I was going to heat the coupling when he talked about the oven.

Merritt,
It's possible that both the machinist and the mechanic you talked to aren't versed in inboards and the need for a heat shrink fit or if they are maybe you didn't follow what they had to say. Reread the thread as suggested. If you mentioned the heat shrink fit to the machinist, he should immediately understand.

It's still possible to do the repair the damage for not much money. Get another coupling half but undersize or "blank bore". Take the shaft and coupling half to the machinist and have him bore the coupling .000" to -.0005" matching the old shaft diameter. As Tom mentioned, all shafting has tolerances plus as mentioned, you old shaft may be worn as well. Even brand new and couplings are bored to match the shaft for the heat shrink fit. You can't just go by the shaft being a 1" diameter.

The key can be found at the hardware store but have the machinist look at the keyway in your old shaft. Since you chewed up your key, the keyway in the shaft may be chewed up as well. If so, it can be machined oversize and then the machinist can make a key to fit.

Merrit, not to beat you up too much or come across as preachy, but everything you need to know was posted several days ago. Pete told you what the problem was and Chris told you how to check and see if any of your old parts can be saved:

8122pbrainard wrote: Your coupling and maybe even the shaft is TRASH. Of course the prop shaft turned easy. The coupling was so fretted that the shaft was loose. The coupling is a heat shrink fit. It's a .000" to a - .0005" fit. The key does NOT handle the torque. The interference fit handles most of it. Your coupling was so fretted that you sheared the key!!!

SNobsessed wrote: Merritt - You will need to measure both the shaft OD & the coupler ID to determine if these parts can be reused. Take 3 measurements (120 deg apart) with a micrometer on the shaft OD, then average them.   Likewise for the ID of the coupler, except you need an internal mic.   A machine shop can help you measure these if you don't have access to the gages.   You need the shaft average to be .001 inch bigger than the coupler ID average (press fit).

Like you said, this website is full of smart people willing to donate their time to help you out... but you have to hold up your end of the bargain! As a teacher, surely you understand that the student shares part of the responsibility in the learning process. If you dont understand something, dont ignore it- ask for clarification. No one is talking above your head on purpose.

Dont understand what a "heat shrink" or "interference fit" is? Ask! (Or you can google it)

Dont have the tools that you need to perform the checks described? Ask for a description and we'll tell you where to get some that wont break your budget. 6" Digital calipers for $16.99

If you determine that you cant save your parts, we'll remind you that you can save 10% on SkiDIM orders.

We'll also give you the information you need to determine the proper shaft length if you buy new... I would NOT recommend ordering a shaft the same length as the one you removed (it is likely too long).

Merritt,
Now you have the general idea for a single taper shaft and coupler which is what your old one was. Here's the basics for that shaft/coupler combination.

I'll try and dummy it down for you as you requested.

You should not be able to fit the shaft and coupler together. The shaft will be noticably larger than the coupler. If the shaft can be inserted into the coupler by hand both are probably junk but taking it to a good machinist who knows something about inboard prop shafts will help to determine if one of them may be fixed or resused. The clearances have been discussed already. Generally, they're junk and just replace both. Chances of fixing are probably not worth the price.

Heat the coupler in an oven to at least 200-225 degrees for at least a half hour. Maybe even 45 minutes.

If you have a freezer big enough, put the shaft in a frezer for at least an hour. Two would be even better.

Now comes the tricky part. Take the couopler while it's still hot and the shaft while it's still cold and fit them together with the slots and key properly aligned and they'll shink/expand together. You will obviously need gloves and please be saftey conscious.

Now you have another problem. You probably fitted them together on a bench someplace. Now you have to get the shaft back in the boat but you probably didn't think that far ahead. The only way the shaft will go back in the boat now is by removing the engine and transmission which is another thread entirely and probably something well beyond your abilities in the timeframes that you've allowed for yourself not to mention the equipment needed to do this task.
Some here have been able to put the shaft/coupler together in the boat but it's obviously much more difficult and needs probably several other pairs of hands to accomplish. Timing is of the esscense when doing this so you need to plan accordingly or remove the engine/tranny. Your choice.

Now with the shaft coupler installed in the boat, you can go through your alignment procedure as you've found elsewhere.

What we generally recommend instead of going through all this stuff is purchasing an ARE double taper shaft and coupler. These are easliy put together in the boat. You don't have to remove the engine or tranny. There is no heating of the coupler, freezing of the shaft or any of the other issues associated with a single taper shaft as they are fit together like the prop fits on the other end of the shaft...a taper fit. Hense the name...double taper shaft. Very easy, very fast and very simple. They are however, more expensive.

So there you have it. Hope this helps you to understand things a bit better.

Hollywood wrote: 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...

Talk about overkill... JB Weld would have worked just fine.

TRBenj wrote: Talk about overkill... JB Weld would have worked just fine.

I forgot to mention, he did that on the first "repair" in the worn out keyway when the set screws came loose. Boat owner said the engine spun but no forward movement. This repair failed during reverse and introduces the prop to the rudder. Talk about hack job!

GlassSeeker wrote: SkiDIM can help you figure out your shaft length

They'll get you close, but I would adjust their measurement (most likely based on the original shaft length) in order to minimize the prop to strut clearance. Shoot for 1/2". It was often way beyond that from the factory- and it will vary from one boat to another. Minimizing this clearance gives you the best performance and reliability, and since ARE makes each shaft to order, it wont cost you a dime extra to get a custom length made for you.

Merritt - Not doubting your determination to get this done, but if you disclose your area maybe a veteran CCF'r is in your city & can stop by to give you some pointers.

Yeah can also be called a "how far down the rabbit hole do you want to go" situation.

You can do it the (not so) quick and (not so) easy way or you can do it all.

The point about the rudder packing is a good one. And the ARE suggestion is good too. It will cost you more but it is piece of mind and a lot less hassle.

The press fit on the coupler isn't a fun job and as was said, it is easier when the engine is out. When the engine is in the way, you have to thread the preferably cold shaft through the strut and mate it with the very hot coupler. You could have the shaft in the strut and envelop the end of it in ice packs instead of putting it in a freezer, as most people wouldn't have a freezer large enough.

In lieu of cooling the shaft, I just heated the coupler on the hot grill for about an hour. It slid right on.

An excellent Minnesota winter project. Ice not needed.

Merritt, I purchased a good prop puller. I would also like to inform you and everyone here that I am willing to let anyone here who needs it to borrow it. All I ask is the borrower pay for the ride and return it in good working order. I posted here a while back to borrow one with no offers, so I figured I would start a loaner program on the one I purchased. Its my contribution for all the help I recieved here.


Also for future reference, this forum is great but sometimes you have to be thick skinned and filter comments that might or might not be sarcastic. Good luck with your boat..

Phil,
Buy a 4" diameter by 3/4" bore and have it bored to match your shaft. After he bores it, he should press the coupling on the shaft and then chuck the shaft up in the lathe. taking a light "shim" cut on the coupling face will ensure the face run true to the bore.

BTW, while you have the shaft out, set it up in V blocks and check it with a dial indicator for straightness. . Your machinist can do it. Don't forget checking the taper at the prop end for straightness.

The shaft may not wobble in the strut. Once you have the shaft out you should be able to look and see if is is wearing straight or not. Mine looked pretty good until the shaft was out, then it was obvious it was running through the strut at an angle.

Theres a bolt in the top of the rudder and a pinch bolt off to the side, that's it. You might have to put a jack under the boat and lift it up off the trailer a little to get the rudder all the way out. That depends on how much room you wave to work with between the prop guard and the rudder. If your close to the lake it may be easier to just slide it back on the trailer a little.