This should help. Split couplings also need to have a fit & face done..
https://marinehowto.com/a-new-prop-shaft/
https://marinehowto.com/a-new-prop-shaft/
Pulling prop shaft off coupling procedures?
- Thread starter JPS27
- Start date
Thank you ALL for all the input. Great site! I also need to update my profile info as I don't have an Ericson 27 any longer. I've got a Pearson 36-2 with a 1.75" diameter shaft.
Are you all saying that if I take the shaft/coupling apart to put on a new shaft log hose that I will need to get the shaft and coupling re-machined for fit? And that I need to lift the engine for readjusting?
I have had a longer "to do" list on this haul out than I was expecting, so taking on tasks that could get more complicated than expected is not an option.
My engine was brand new as of September 2022 and the couplings look practically brand new, no visible rust. If all of those tasks are required tasks, then I'll probably skip the new hose replacement since it looks old, but solid. If I can get it apart and put it back together I might go ahead. I figured I could check the alignment fairly straightforwardly too.
Are you all saying that if I take the shaft/coupling apart to put on a new shaft log hose that I will need to get the shaft and coupling re-machined for fit? And that I need to lift the engine for readjusting?
I have had a longer "to do" list on this haul out than I was expecting, so taking on tasks that could get more complicated than expected is not an option.
My engine was brand new as of September 2022 and the couplings look practically brand new, no visible rust. If all of those tasks are required tasks, then I'll probably skip the new hose replacement since it looks old, but solid. If I can get it apart and put it back together I might go ahead. I figured I could check the alignment fairly straightforwardly too.
Most (all?) us would not lift the engine to reinstall the shaft. Because if the shaft is completely removed, it will probably be necessary to drop the rudder too, really more work than you want to get into. Best practice is to have the shaft and coupling fit and faced. However, I doubt many boats have done that after they left the factory.
If after reinstalling the shaft you can not get it aligned, then it may be necessary to get the shaft and coupling fit and faced.
Assuming the alignment is within a few thousandths you should be OK, not perfect, but ok. The boat probably won't sink. If the stuffing box hose fails, there is a good chance the boat will take on a lot of water which you won't be able to bail out fast enough. You know where that will lead.
It is your boat, make the choices that matter most to you. Remember the first rule of boating is to keep the water out of the boat.
If after reinstalling the shaft you can not get it aligned, then it may be necessary to get the shaft and coupling fit and faced.
Assuming the alignment is within a few thousandths you should be OK, not perfect, but ok. The boat probably won't sink. If the stuffing box hose fails, there is a good chance the boat will take on a lot of water which you won't be able to bail out fast enough. You know where that will lead.
It is your boat, make the choices that matter most to you. Remember the first rule of boating is to keep the water out of the boat.
Since I was going to be on the hard longer than planned, my thought was to add this "little" project to the list. To replace the shaft log hose would require creating about 6 inches of space from the transmission side coupling. I have plenty of space inside the boat and outside for that maneuver. I guess I can't wrap my head around why this project would require re-facing and re-fitting the shaft coupling to the shaft. I'm no expert on alignment, but I've done it a few times and then get a local expert to check my work.
I would separate the shaft and coupling, and if necessary mark the shaft & coupling so you put them cap back together the same way…but the key should do that for you.
Then replace the stuffing box hose (or switch to the Volvo Penta seal!).
Greg
Then replace the stuffing box hose (or switch to the Volvo Penta seal!).
Greg
You might be headed in the best direction if you're willing to take a chance.
1) Start by checking the trueness of the existing flange to the prop shaft. Start with Fig. 1c in the attachment. You might also want to check the alignment of the Xmission to the prop shaft flanges to see if you can reproduce the same results again.
2) Score the prop shaft flange and the shaft so they go back together the same as they came apart.
3) Replace the hose and anything else that is required.
4) Replace the flange on the prop shaft and once again measure the trueness of the flange to the shaft. This is the acid test. Did it go back together or is it now out of whack ?
5) See if you can get the angular alignment of the two flanges (prop and xmission) back to what it was before disassembling.
If the flange is once again true to the shaft, you're in luck. If not, it's off to the machine shop.
If you've aligned your flange before you will see you have some decisions to make in this process before proceeding to the next step.
If you do this, could you please report what your readings are as I have not been able to find anything on the accuracy of replacing either solid or split couplings without resurfacing. It would be nice if they would hold their trueness.
Thanks for this information. I'll let you know what I end up doing. The document is very helpful.
What's even better with that document, if you're having trouble falling asleep at night, it'll put you out faster than laughing gas
.Having had a boat where a previous owner replaced the pss seal and the coupling managed to loosen on the shaft during my ownership, I've never felt comfortable just reinstalling things and hoping the fit is tight enough and true the second time around.
Once fit and faced, it's a tap fit and it's not a big deal to get things back together. I've only done a couple of these, but on my current boat (Catalina 350) the only way to get the shaft by the rudder is with the cutlass bearing out first. Without getting too long winded here, bottom line is that was a no go (it isn't in a strut on a Catalina 350 and it had a plastic shell, not brass). Since that was the first thing I tried, the sawzall came out immediately and I wasted no time trying to get the coupling off and the shaft out (it came out in 3 pieces). Too bad in a way, as I had lots of room to work as I had already pulled the transmission to replace the damper. I bought the new stuff and had it fit and faced before it was shipped. So it helps if you can find out the details related to shaft removal on your particular boat, and have a plan A and a plan B before you even start.
Once fit and faced, it's a tap fit and it's not a big deal to get things back together. I've only done a couple of these, but on my current boat (Catalina 350) the only way to get the shaft by the rudder is with the cutlass bearing out first. Without getting too long winded here, bottom line is that was a no go (it isn't in a strut on a Catalina 350 and it had a plastic shell, not brass). Since that was the first thing I tried, the sawzall came out immediately and I wasted no time trying to get the coupling off and the shaft out (it came out in 3 pieces). Too bad in a way, as I had lots of room to work as I had already pulled the transmission to replace the damper. I bought the new stuff and had it fit and faced before it was shipped. So it helps if you can find out the details related to shaft removal on your particular boat, and have a plan A and a plan B before you even start.
Did you disassemble the shaft and flange coupling before you placed them back in the boat or raise the engine and slide them in, in one piece ?
If you disassembled them before installing, what was trueness between the prop shaft and flange coupling or did you avoid checking out of fear for what you'd find ?
How did the final alignment of the whole schmear look when you were finished ?
Disassembled.
This is the first I've ever heard of having to slide it in as a unit, so no, didn't check.
Final alignment <= .002". Haven't checked it in 2 or 3 years. Probably should this season.
Thanks. Good to know. Than shows if you're careful it will retain its trueness after the flange being on, off, and on again. I would imagine if no great forces are encountered, it should remain true.
When I replaced my coupling and stiffing box, I slid the shaft out aft. Did not have to drop the rudder. Brought it to the prop shop and they fit a new coupling. I slid the shaft back into place, then put the coupling back on and all was well. Alignment was done after and worked out perfectly.
If I remember right, they sent the shaft with the coupling on it and plastic wrapped up. The set screw bolts were not installed. I assumed this was sent that way to protect the pieces in shipping. I just carefully tapped the shaft out and put it back together after the install.
I think the problems show up later when the assembly has been together for a long time. Lots of force may be needed, heat possibly, and especially on saltwater boats, a rust bead gets broken. All makes for a less likely chance of getting things back together true, and having the tight fit needed to keep it that way.
Heya, heya, heya ! ! !
Step right up ladies and gentlemen. See if you can get the coupling back on the shaft with the same level of accuracy as before the coupling was removed.
Unfortunately, not every one's a winner. You lose ? You haul it all out again and cart it off to the machine shop to have it faced.
Yup. I think that's the telltale if it's worth trying to reinstall without resurfacing.
For a one piece coupling If the shaft and the bore are a wring fit or a very light interference (.0002 dia.) then the bore and the shaft are concentric and have the same centerline. The only variable then is squareness of the flange to the bore of the coupling. Hard to see how it will change when assembled.
For a split coupling you add in variables like how tight are the screws holding the coupling together, but assuming you mark the shaft and coupling positions with a scribe mark and use a good torque wrench on the screws reassembly should be possible within the tolerances required. You can also use a flexible coupling for a little more forgiveness.
For a split coupling you add in variables like how tight are the screws holding the coupling together, but assuming you mark the shaft and coupling positions with a scribe mark and use a good torque wrench on the screws reassembly should be possible within the tolerances required. You can also use a flexible coupling for a little more forgiveness.