Stern Tube Too long - Extends into Bellows

[Strgzr]

Interesting. so when you installed the split coupling, did you get it "faced" on a lathe. If so, was the shaft attached or not.

Thx,
MP

[william vanwagoner]

As I recall the yard pulled the shaft by sliding it past the rudder and sent it along with the split coupling to a machine shop where they machined it to fit properly. You might want to check in to the Sigmadrive: (sales@bruntons-propellers.com or Google sigmadrive) which does not appear to need any machining and essentially removes the need to do a fine alignment. It is quite expensive but might get a lot cheaper when you start adding up machine shop costs and yard labor.

[william vanwagoner]

As I recall the yard pulled the shaft by sliding it past the rudder and sent it along with the split coupling to a machine shop where they machined it to fit properly. You might want to check in to the Sigmadrive: (sales@bruntons-propellers.com or Google sigmadrive) which does not appear to need any machining and essentially removes the need to do a fine alignment. It is quite expensive but might get a lot cheaper when you start adding up machine shop costs and yard labor.

[william vanwagoner]

Here is my split coupling. Please pardon lack of transmission as it was shot during damper replacement

20200508_161408.jpg (213.29 KiB) Viewed 2695 times

[Olivia Mae]

Hi all,

I'm going to add my 2 cents in on the discussion about the need to replace the coupling when doing work on the PSS seal. I'm well aware that many people don't. At the minimum, it should be sent with the shaft to a marine machine shop to be checked and fitted and faced. The reason is that even though it seems to go back together fine, the press fit clearance may be off after disassembly. The danger is having it loosen up at a later date. I had this happen on our other boat, a Seaward 25. The previous owner had replaced the PSS seal and reused the coupling. It loosened up on the shaft a couple of years later. Tightening things up caused excess vibration, and I ended up travelling several hours in Ontario to the closest marine machine shop in the province to get a new shaft, coupling, and cutless while we were supposed to be having fun on vacation.

Currently, the transmission, prop, cutless bearing, and PSS seal are out of our 350. I had to have the transmission rebuilt this winter, and pulled the damper plate, cutless, and PSS seal as well for replacement as it is a 2003 boat and they were original. I read that you could get the prop shaft past the rudder if the cutless bearing was out of the way first. Unfortunately, I couldn't get the old cutless out first as it had the plastic outer sleeve that just crumbled when I tried to get hold of the exposed end with pliers. I didn't waste time trying to get the coupling or prop off, decided to cut the shaft instead twice (it came out in 3 pieces). I removed the prop on a press later. In my case, the cost of a new shaft was worth the aggrivation that I knew I faced getting everything apart, especially if the rudder had to be dropped or the motor lifted to get the shaft out anyway. I just hope my info is correct and I can get that new shaft back in when we head north to finish the repairs!

Here are a couple of links below to a great site on marine repair. In both, I think you'll see some info on why the coupling should be replaced and what is done when they fit and face it in a shop.

https://marinehowto.com/installing-a-pss-shaft-seal/

https://marinehowto.com/new-prop-shaft/

Scott

[wolfe10]

Scott,

Guess I am having trouble understanding need to resurface/true the shaft coupling:

Using original shaft, original coupling, mark original shaft and transmission couplings so they can return them to their original orientation.

And, starting the shaft coupling onto the shaft by hand, NO WAY that the key way was not lined up-- clearly it would not start on the shaft by hand if not lined up.

Now, if the shaft coupling easily slips on, I would agree a no go. But, ours was a hard press fit. 400 hours later, all is well.

Does engine alignment need to be checked-- yes. It is a part of preventive maintenance just as is snugging the engine mount bolts!

Sure, if using a new/different coupling, machining on the shaft is an excellent idea.

[Olivia Mae]

Hi Brett,

As I mentioned above, I know many times the job is done (even by yards) where the coupling isn't replaced and is reused. Sometimes it works, sometimes it doesn't. Since the spec for the clearance is likely less than 2 thousanths (which is almost impossible for me to measure accurately with my vernier caliper), I know I can't tell if the tap clearance (whatever that is in machinist's terms) is within spec. Add a little corrosion to the coupling and it's even harder to tell. Had I not had the experience with our other boat, I might not really care. I have no idea what that fit felt like to the previous owner, all I know is the mess I found when I noticed the problem a couple of years later.

So, with that history in mind, and the research I had done on the way this job is "supposed" to be done, I just wouldn't risk reusing the coupling on my own boat. The price of a new coupling and machine work is way less than the cost later if things go wrong.

On the 350, this does open a can of worms. Since the shaft likely won't clear the rudder without the cutless bearing removed first, pulling the shaft out might be no easy job. Just putting in a new PSS seal seems easy enough, but no matter how you plan the job, you still may end up with having to put in everything new. I just chose to go that route rather than deal with the time and frustration of trying to save parts.