Keyway on shaft by coupler

As long as it is still seated and held firmly in place in the keyway, there is no real issue with it sticking out a bit past the coupler. Just make sure that it's not working its way out because the assembly is loose, because that will lead to shaft damage.

Skip:
That keyway should be flush or close to it. 1/2" is a lot. I had one pop out about 18 miles out of Masonboro inlet on a 45 Viking. You don't want that to happen it is a real PIA. Do you have any vibration while running? If so you may want to have the wheels and rudders checked for damage. It may have caused the keyway to work it's way loose.

Before you get too worried, take a punch or a screwdriver and see if you can tap the key back towards the coupling. If it moves you need to find out why it is loose. If it is solid, you don't have a problem. Not all keys are the same length and sometimes a replacement key is much longer than the coupling.

Make sure the shaft is tight inside the coupler as well. Sometimes when the key is sticking out it's because the shaft has backed out a bit. That's the prime concern.

Good advice.

You can check that quickly by looking closely at the shaft just behind the coupling half, it should not show a "ring" or witness mark where it used to meet the coupling and should not show any longitudinal scratches from being pulled out. If you have any doubt then you are back to disconnecting the coupling half and inspecting it.

Does your coupling half have a setscrew? If so, it is probably loose and the key is slightly undersized or the keyway on the coupling half is slighly oversized or worn.

It is difficult to give advice on what to do without actually being there to evaluate it "hands on" but if the key moved back in place easily without much force then I would be inclined to pull the coupling half and fit a new key that fits very snugly.

The key prevents the coupling half from rotating on the shaft and a loose key will allow the coupling to rock back and forth with firing impulses and loads until the fit between the coupling and the shaft wears enough to cause real problems. You may have seen keys that have a shear line along the shaft OD and that is caused by the relative motion between coupling and shaft. It shows just how much force may be transmitted by the key under load so you can see how important a tight fit really is.

It might seem like a real pain to disconnect the coupling but it shouldn't alter the alignment and it will give you a lot more confidence in the connection as well as reduce the risk of more expensive damage down the coast a bit.

Good luck and keep us posted.

That's a good sign, it or they might just be loose or were never tightened. If they are loose, remove them completely and put them back in with Loctite. It will not be much fun removing them next time but nothing a little heat won't solve.

Or, use setscrews in tandem like prop nuts if you have the depth.

If you do any distance cruising or have not checked the alignment is a few years I recommended you check it. You can be out of alignment without noticeable vibration. Run the engine in gear and watch the shaft, if it blurs you have a problem. Poor alignment can cause many problems including oil leaks, shaft breakage, strut damage, bearing and drive failure…

Check the shaft flange faces; they should be parallel at operating temperature to .00015”. If you have a flexible coupler alignment is still important as they are a dampener not a universal joint. Remove the flange from the shaft (this should be difficult) and inspect all matting surfaces, use a new key and make sure it fits very snug in both shaft and flange separately. Reassemble and align. Repeat for your other engine.

Proper alignment is not as simple as it sounds so I recommend you have it serviced by a professional. Your boat is an expensive toy so take good care of it.

Good luck

Going boating with a known potential problem is no fun.
Would you go flying with your friend if he told you “that’s a little lose but I don’t think it will fail today”?

I think you have a decimal misplaced, that is equal to .003 mm and is about 25 times better than acceptable.

For an out of alignment shaft to blur it would have to be really far out. When CSkipR pulls the bolts and shifts the shaft back he will know instantly if there is an alignment problem and can measure it before doing anything else.

Your correct, I meant .0015"

I have seen long shafts blur at just .010 off at the coupler flange.

The difference is determined by the size of the shaft- larger shafts mean larger acceptable differences. I could not tell exactly what the talk was about early in the thread when folks were referring to the key as the "keyway". The shafts' keyways ought to be the same but the length sticking out of the coupling is not a area of importance as long as the key cannot work it's way out. On a 45 Viking the coupling is held onto the shaft (2 1/2 inch) with three allen head grade 8 bolts that are wire tied to each other so as not to vibrate loose IIRC. The coupling ought to be secured to the shaft so that hydraulic portapower is needed to break it loose- if not, as Henning said, this is an issue.