Shaft to flange connection...

[aqfishing]

Originally Posted by ProjectManaia

I assume (very well aware that assumption is the mother of all mess-ups) that the replacement bolt put in 2 weeks ago was weaker than the original. I know the replacement was simple galvanised steel...
I am currently tied up right next to a machine shop so we are in the right place to get those things done.... my big hope however is being bale to sort things out without lifting the boat out (crane looks dodgy as something else) .... so fingers crossed and hope for the best

Hi,

I would say just put a high tensile steel bolt back.
There seems to be some sort of shock system in the coupling.

[ProjectManaia]

Originally Posted by kmacdonald

Now for the bad news. The rudder may have to be removed to remove the shaft. The keyway and key must be machined to close tolerances. You cant "grind them".

well aware of that... IF the shaft has to go out the boat is on the hard either way and then (thanks to a smart setup) it is easy to remove the rudder. Just 8 bolts, since it is sitting on the extended keel on the bottom and the rudder shaft on the top, which can still stay in place.... at least some good news along the bad streak

[kmacdonald]

It looks like there are set bolt dimples drilled in other locations on the shaft indicating previous issues.

[ProjectManaia]

Originally Posted by aqfishing

Hi,

I would say just put a high tensile steel bolt back.
There seems to be some sort of shock system in the coupling.

Sort of two shock systems: one is the "rubber flange" in between the flanges and the second one is the smooth hydraulic gearbox... in combination they should be able to do the trick - one would hope

[ProjectManaia]

Originally Posted by kmacdonald

It looks like there are set bolt dimples drilled in other locations on the shaft indicating previous issues.

I believe that the drilled hole is where the original bolt was sitting. the replacement was then. put into the key slot - not an ideal solution in my humble opinion - but I am more of a rig guy than an engine guy... still have to catch up on that wisdom

[Jackg]

Can't stress enough the importance of a *hardened* bolt that goes into a dimple in the prop shaft. You need to machine that dimple into the shaft if it's not there. And there should be a hole in the hardened bolt through which you run wire, and the wire goes around another bolt or the coupling, so the hardened bolt can't back out.

[ProjectManaia]

Originally Posted by Jackg

Can't stress enough the importance of a *hardened* bolt that goes into a dimple in the prop shaft. You need to machine that dimple into the shaft if it's not there. And there should be a hole in the hardened bolt through which you run wire, and the wire goes around another bolt or the coupling, so the hardened bolt can't back out.

Like the thinking.... especially the wire part to secure things.
Thanks for the hint!

[kmacdonald]

Originally Posted by ProjectManaia

Sort of two shock systems: one is the "rubber flange" in between the flanges and the second one is the smooth hydraulic gearbox... in combination they should be able to do the trick - one would hope

The damper plate on the flywheel absorbs the torsional shock loads.

[wingless]

Originally Posted by kmacdonald

Now for the bad news. The rudder may have to be removed to remove the shaft. The keyway and key must be machined to close tolerances. You cant "grind them".

On my boat both shafts can be removed / replaced by centering the rudders, sliding out past the rudder w/ sufficient clearance.

[stormalong]

The shaft has a key slot cut into it. They are standard dimension keys. Usually in 1/16th of an inch increments. Easily measured. Have you looked closely and confirmed that there is no slot in the coupler? Is it possible that two weeks ago the shaft pulled out and the key dropped into the bilge?

The shaft does not need to come out. If the coupler needs to have a slot cut it is done with a broach and a hydraulic press. The broach is a long cutting tool that is pressed into the coupler to cut the slot. The coupler has to be removed from the boat.

If the machine shop is telling you the shaft has to come out find another machine shop.

[MicHughV]

I totally agree with the above post.....both coupler flange and the shaft should have a keyway ground into both. 100% certain about that!!!. No ifs, ands and buts about it. A keyway is a long square groove, cut into both shaft and flange.

It will be there !! I promise....it will be there !!!

If you can pull the shaft out a bit ( maybe 3" or so) you will see the groove for the key. Don't pull the shaft out too much and support it while it's out, to prevent unnecessary leaking or movement at the packing gland. That shaft groove needs to line up with the groove inside the flange, and then you need to insert a key in that groove first. Those keys are pretty standardized.....maybe 2-3" long x 3/16" x 3/16...or 2-3" x 1/4" x 1/4" or something close to that. You should be able to measure this.

Some keys are metric!!

It will be a tight fit and may require you to hammer it in.
Those keys are standard and you may be able to find them at you local hardware store or online or other marine or engine store.

Once the shaft is back in (with key) , you can re-insert that bolt. Typically that bolt will screw into an indent in the shaft. Once you pull the shaft out the 3" or so as described above, you should see the " indent". This looks like a shallow hollow drilled into the side of the shaft to allow the bolt to lock into it. That bolt has only one purpose, which is to keep the shaft inside the flange when you reverse.
Some flanges/shaft will have two bolts.

It is imperative that you prevent that bolt from vibrating out. You can lock it into place with a wire tie, or a small hose clamp around the head of the bolt, with the end of the hose clamp lead jammed against the flange. Be careful to install that hose clamp so if the bolt does try to unscrew, it will tighten up. ie, there is a right way and a wrong way to do this.
I've also seen a large hose clamp installed right around the flange.
That bolt should have a small hole drilled thru' the head. If not, drill it yourself and use stainless steel wire to go thru' that hole and then wind the wire in such a manner that the bolt can't unscrew itself, or use the hose clamp.

Now onto part two. How did all this happen in the first place?? Once you have the flange firmly back in place on the shaft, remove the entire flange from the engine coupler....the gap between the engine flange and the shaft flange should be near as damnit to zero...ok, maybe a few 0.0001" difference, but no more. If it's more, you have an alignment problem, a topic for another conversation, or it could be a worn cutlass bearing, see below.

And finally, you may have a problem elsewhere, which would be the shaft bearing right in front of the prop, called a cutlass bearing.. You will need to dive on the shaft to view this. If the shaft can jiggle inside this bearing, you have a problem and that bearing needs to be replaced. Maybe the shaft as well.
Sometimes this can be done underwater, if you have no other options, with the understanding that if you screw this up, there can be a lot of water coming inside your boat. It takes a lot of planning and some skill, a lot of
skill !!

The same goes for the above "key"explanation, it can be done with boat in the water, but if you don't feel qualified to do this, either have a professional do it for you or have the boat hauled.

Your best bet, would be to have the boat pulled and do it on the hard.

Good luck !

[jamhass]

Originally Posted by DougR

From the looks of the photo, there is a serious amount of misalignment between the gearbox output flange and the prop shaft flange. This misalignment will cause constant flexing in the flex coupling and constant working of the propshaft flange on the shaft, fatiguing the pin and everything else. Likewise if the bolt isn’t a high strength bolt with a tight fit in both the shaft and coupling it will shear.

It ‘s time to have a skilled tech check the engine alignment and the prop shaft to shaft coupling interface for issues.

Looks like a flexible (elastomeric) coupling to me.

[ProjectManaia]

Originally Posted by MicHughV

I totally agree with the above post.....both coupler flange and the shaft should have a keyway ground into both. 100% certain about that!!!. No ifs, ands and buts about it. A keyway is a long square groove, cut into both shaft and flange.

It will be there !! I promise....it will be there !!!

If you can pull the shaft out a bit ( maybe 3" or so) you will see the groove for the key. Don't pull the shaft out too much and support it while it's out, to prevent unnecessary leaking or movement at the packing gland. That shaft groove needs to line up with the groove inside the flange, and then you need to insert a key in that groove first. Those keys are pretty standardized.....maybe 2-3" long x 3/16" x 3/16...or 2-3" x 1/4" x 1/4" or something close to that. You should be able to measure this.

Some keys are metric!!

It will be a tight fit and may require you to hammer it in.
Those keys are standard and you may be able to find them at you local hardware store or online or other marine or engine store.

Once the shaft is back in (with key) , you can re-insert that bolt. Typically that bolt will screw into an indent in the shaft. Once you pull the shaft out the 3" or so as described above, you should see the " indent". This looks like a shallow hollow drilled into the side of the shaft to allow the bolt to lock into it. That bolt has only one purpose, which is to keep the shaft inside the flange when you reverse.
Some flanges/shaft will have two bolts.

It is imperative that you prevent that bolt from vibrating out. You can lock it into place with a wire tie, or a small hose clamp around the head of the bolt, with the end of the hose clamp lead jammed against the flange. Be careful to install that hose clamp so if the bolt does try to unscrew, it will tighten up. ie, there is a right way and a wrong way to do this.
I've also seen a large hose clamp installed right around the flange.
That bolt should have a small hole drilled thru' the head. If not, drill it yourself and use stainless steel wire to go thru' that hole and then wind the wire in such a manner that the bolt can't unscrew itself, or use the hose clamp.

Now onto part two. How did all this happen in the first place?? Once you have the flange firmly back in place on the shaft, remove the entire flange from the engine coupler....the gap between the engine flange and the shaft flange should be near as damnit to zero...ok, maybe a few 0.0001" difference, but no more. If it's more, you have an alignment problem, a topic for another conversation, or it could be a worn cutlass bearing, see below.

And finally, you may have a problem elsewhere, which would be the shaft bearing right in front of the prop, called a cutlass bearing.. You will need to dive on the shaft to view this. If the shaft can jiggle inside this bearing, you have a problem and that bearing needs to be replaced. Maybe the shaft as well.
Sometimes this can be done underwater, if you have no other options, with the understanding that if you screw this up, there can be a lot of water coming inside your boat. It takes a lot of planning and some skill, a lot of
skill !!

The same goes for the above "key"explanation, it can be done with boat in the water, but if you don't feel qualified to do this, either have a professional do it for you or have the boat hauled.

Your best bet, would be to have the boat pulled and do it on the hard.

Good luck !

Thank you for this! Most of what you write was my thinking already. I do have the professional coming over in an hour or so, I do know a fair bit about boats but this is new land for me therefore I prefer to have someone with a better idea at least leading the job and I am more than happy to do the dirty work around it. Let's see what he says but at least I got some good input to throw in as well now....
Thanks again!

[Pizzazz]

A couple of points. When I was replacing the shaft and the coupling, I was told by the manufacturer that you cannot easily put the coupling on the shaft on the boat. The coupling is typically pressed on the shaft, and yes, there must be a key. If your coupling is loose, there will be a play and shaft alignment will be difficult to impossible. The proper way to do this is to lift the engine and slide the coupling and the shaft out below the engine. Then you take it to a shop where they press the coupling with the key or just get new parts then insert and align the engine. After the engine is aligned you slide the shaft back and insert your dampener.

If you need a quick fix, I will just use a drill to make a sizable pit in the shaft, go at least 1/8 of the diameter deep and screw in a high tensile boat, secured with a wire as discussed above. This will not be as strong as a key but good enough until the next haul out. May be put two bolts opposite each other.

SV Pizzazz

[MicHughV]

it's hard to evaluate these things from some photo's and a written description, but a couple of things I noted from the pics.......

a) right behind the shaft flange appears to be a european type dripless shaft packing gland, that big black blob of material, it appears to be very close to the prop flange, so that trying to pull the shaft back , even a few inches stands a chance of pushing it thru' that seal...and ...poof...instant water inside the boat.
b) you may have to reverse the order of doing things, ie, remover the shaft flange from the engine flange. Before doing that, put a set of vice-grips on the shaft right behind the shaft flange, and set them tight. Real tight !! Then you can push both shaft and coupler back. The vice-grips will prevent the shaft from going to far back and thru' that seal. Then remove the flange by pulling the flange forward off the shaft.
c) I note in the first photo, there appears to be a " straight line" near the bottom of the shaft indicating the presence of a key way cut.
d) I also note on photo two that the shaft coupler has another bolt hole at 90 degrees to the one with the bolt in it. I have seen this, where the bolt holes are 90 degrees apart and sometimes 180 degrees. If they are 90 degrees, the one hole will be set a bit forward of the other one.

wish I was there to help, but consider the above...