Control the Shaft - Keeping Everything Turning Smoothly
or "What Alignment? "
- Poor alignment
- Stuffing box too tight
- Loose prop (not lapped or not tightened)
- Poor bonding or letting zincs go too long
Once the prop is off, we will inspect and remove the shaft (if you're hauled out). Working with the shaft in the water is impractical - not to say impossible but beyond the scope of this article and beyond the prudent mariner.
The best way is to pull it with a slide hammer. Failing that, you can do it the hard way.
|Doing it the hard way|
Detach the coupler, insert a socket of same or smaller size than shaft, find longer coupler bolts, reconnect it (don’t miss with the socket) and slowly push the shaft out of the coupler by tightening alternating bolts a few turns at a time. This takes forever, but once the shaft is out of the coupler, you can ease it out the rest of the way relatively easily.
|A shaft that has been worn by the cutlass bearing from a bad alignment|
Once it’s the shaft is out, look for excessive wear where the cutlass bearing rubs, and where the stuffing box rubs. In particular, if the shaft is missing a lot of material at the stuffing box, you may not be able to get a watertight seal. Next step is to check it for straightness. Best to have a shop do this – however, if you’re a machinist set it up on a pair of rollers, and mic it for round. More than .004 is a bent shaft. If you don’t know what this means, don’t mess with it.
Check the keyways at both ends to see if they are gouged or scored – we will talk more about keys later. Often a poorly tightened propeller will give you hammering, scoring along the sides of the key or keyway that can become a sheared key or permanently damaged prop/shaft connection.
What the yard has that you don’t have –
Slide hammer to pull shafts quickly and cleanly:
- You can use a socket for the correct size, long bolts, elbow grease and infinite patience.
- You shouldn’t because it will take you a long time and bloody knuckles, and if you miss with the socket you can damage the coupler.
|A slide hammer on the left, and torches on the bottom|
Next we will look at the strut and cutlass bearing
If you haven't checked your prop, check it out now
If you would like to use the content of these articles, please contact us.