Reversing gear problem

[Wisakedjack]

Hi, guys. I bought 1976 Catalina 30 with Atomic 4 engine this past spring. PO did a lot of work on the engine including rebuild and getting rebuilt gear box. I had few minor issues that I was able to resolve using help from this forum. Many thanks for building such a helpful community and an excellent resource.

Today while coming back to the mooring after a day of sail I was reversing the boat when I heard the change in the engine sound and noticed that propeller shaft was no longer spinning. When I got a chance to inspect the gear box I've noticed that rear coupling shifted aft, so that the tail shaft became visible. I am attaching a picture of what it looks like now:



If I hold the read coupling by hand I can slide the tail shaft back into the back of the reversing gear assembly by few inches without much effort. No unusual loud noises were heard when this happened. I am wondering if anyone could make a suggestion on what is the issue here and what it would take to fix it. Any advise would be greatly appreciated. Many thanks.

[Mo]

Haven't had to deal with one but heard of it. Couple of things you could / should do.
-ensure the keyway is still intact.
-there should be a set screw (or two) on the coupling itself.

My efforts would be ensuring the keyway is there and working. Then get the shaft back in.

Next I would remove the set screw and drill an indent hole into the shaft...maybe 1/8 inch. Be careful not to tear up threads...do for both set screws. Put screws back in with lock-tite.

There is also a two piece couple on this site MMI catologue that might be an option for you.

[Al Schober]

The shaft coupling is bolted to the transmission flange with 3 bolts. If you remove those bolts, you'll be able to slide the shaft & coupling aft and the transmission flange forward. When you do this, I think you'll find that the nut on the aft end of transmission shaft has come off. The repair could be as easy as reinstalling the nut with a new locking washer. If the threads are damaged, things could get more involved. Oh yeah, there's a key between the flange and the transmission shaft - don't lose it.

[Mo]

Originally Posted by Al Schober

The shaft coupling is bolted to the transmission flange with 3 bolts. If you remove those bolts, you'll be able to slide the shaft & coupling aft and the transmission flange forward. When you do this, I think you'll find that the nut on the aft end of transmission shaft has come off. The repair could be as easy as reinstalling the nut with a new locking washer. If the threads are damaged, things could get more involved. Oh yeah, there's a key between the flange and the transmission shaft - don't lose it.

Here's a couple of pics from engines I have sitting in my garage. You can see where the coupler bolts on. I wonder if the bolts were long enough in the first place? I don't see any thread out of the bolts on the coupler where they'd go into the transmission tail flange. The upper pic is of my spare and it has reduction gear...the lower pic is without a reduction gear and should be the same as yours.

[Al Schober]

Here's a picture of the transmission flange showing the big nut in question. I think your nut has come off the tailshaft. Note that in the photo, the 3 ears on the lockwasher have NOT been bent over to retain the nut. When you unbolt the shaft coupling, the washer and the nut should be right there and will probably drop out.

[Mo]

Al, you are right...I can't see anything else there that could have occurred. The nut must be sitting inside the coupling and flange...might even still be on the shaft in place. Just wondering if that shaft will slide right back into place in the gear box without having to open it up?? Must be something that holds the end of the shaft inside the gear box though??


If the whole shaft moved back must have lost pins itn holding arms or maybe they weren't even in there. https://www.youtube.com/watch?v=K4CCzYqctv0

[JOHN COOKSON]

Wisakedjack
I can't help you with the trany problem but I would like to extend a big welcome to the forum.

TRUE GRIT

[hanleyclifford]

The good news is that your couplings look clean and new - should be easy to separate. Please take a picture of what you find when you take it apart.

[Wisakedjack]

Many thanks for all the comments. I will try your suggestions when I get back to the boat next time. I will keep you posted on my progress

[lat 64]

I'll bet a venti grande skinny mocha latte that the nut is still on a bench somewhere.

Welcome.

Russ

[Mo]

Might be Russ...but I think it is on the shaft and the little metal corner tapped up on it to prevent it from backing off. Looks like the whole shaft came back...I hope it's an easy repair regardless.

[hanleyclifford]

Originally Posted by Mo

Might be Russ...but I think it is on the shaft and the little metal corner tapped up on it to prevent it from backing off. Looks like the whole shaft came back...I hope it's an easy repair regardless.

That was my initial reaction, too; but then I saw the key. If the whole shaft came aft the key would still be in the coupling.

[hanleyclifford]

Originally Posted by lat 64

I'll bet a venti grande skinny mocha latte that the nut is still on a bench somewhere.

Welcome.

Russ

That is a dark thought, Russ - which I share.

[Al Schober]

No, you have to remove the big ball bearing before the tailshaft can come aft. The tailshaft forward of the bearing is a larger diameter. I think all that's come aft is the flange piece with the nose that goes into the bearing and the seal. Sliding it back in may take a little wiggle to get it into the bearing. Again, make sure the key is in place.
I've got a drawing here from Paragon Power - perhaps I can scan it. Too bad it's not in the Moyer Manual.

[Al Schober]

OK, here a scan of the area in question. Took longer than expected, as I had to download the right printer software for my newest computer.
Remove three bolts and the shaft and coupling will slide aft together. This will expose the aft face of the transmission flange. As the drawing shows, that piece goes forward through the seal and into the bearing. It has to be keyed to the tailshaft to carry the torque. Forward of the bearing is a large washer and a step in the tailshaft, keeping the tailshaft from moving aft.

[Administrator]

Chapter 6 in the MMI Manual has a detailed explanation and pictorial of the reversing gear used in the Atomic 4.

Bill

[Mo]

Good to hear...if it's only nut backed off and a few bolts that's great.

[Wisakedjack]

I just got back from the boat, so here is an update on my situation. Al Schlober comment was right on the money. When I removed three bolts from the coupling and moved them apart I did find the nut and washer inside. So, it looks like it just came off. Washer ears were not bent (see picture):



Upon examining the output coupling I found the key still inside in the groove (see below):



When I tried to wiggle it over the transmission shaft it did not go all the in. Here is as far as I could get it without using any tools or applying too much force:



So, I've left things as is for now hoping to get more advise. so, here are my questions:

1. The nut thread seems to be ok, so its just a matter of pushing output coupling in place and having nut and washer installed properly with washer ears bent properly. What is the best way to put coupling back in place aside from wiggling?

2. I've noticed that oil came out of the transmission box. Do I need to add more oil and if so how do I do that?

3. As the propeller shaft moved aft a bit I've noticed little water sipping from the staffing box. There was some water in the bulge since I've left the boat yesterday. Is this a concern? I will be away for few days and won't be able to check on the boat. The coupling flang on the prop shaft looks secure and I don't suppose the prop would slide out.

Once, again thank you all for the advise. I am definitely moving in the right direction and fix seems to be in sight.

[Al Schober]

Well, it looks like only one tab was bent over and that one broke off.
First make sure the key is aligned with the keyway in the tailshaft. Then some judicious wiggling & tapping should get it back into place. Then you can see if the nut goes onto the threads - threads in either piece may be damaged. New nut if needed. If the tailshaft threads are damaged, a 3-corner file will help - also something called a thread comb from the auto parts store. The thread combs come in a set with different thread pitches.
Before you make up the shaft coupling, check the alignment with feeler gauges. Good chance to see if you need an engine alignment.
Fill oil to the mark on the dipstick. Evaluate the stuffing box after making up the coupling. Shouldn't drip with shaft stationary - few drops a minute with the shaft turning.

[Wisakedjack]

Al, many thanks for your advise. I will proceed as you've suggested and post here the results. It may be few days till I get a chance to get back on the boat.

[hanleyclifford]

It is possible the key or keyway suffered some damage as the coupling disengaged so it would be a good idea to remove the key and have a close look, maybe even replace it.

[hanleyclifford]

This may be of some help:

[hanleyclifford]

Al - What do you think? Since the key came off with the coupling , is it possible that spacer could have slipped off?

[Al Schober]

Interesting to note the differences between that photo and the drawing. Drawing shows a taper on the fwd side of the flange. Drawing doesn't show that raised area on the tailshaft.

[Jim Creech]

Just having rebuilt my Paragon OXKB I can say with reasonable certainty that there is no way for the gearbox internals to back out unless :
1) The bearing has been completely destroyed or:
2) the raised area on the shaft has completely worn away.
Both scenarios are highly unlikely.
The most likely fix is to clean up the hub and shaft and remove any burrs that may be present. Lightly grease the hub and reinstall onto the shaft with the key ways aligned, install the key, tabbed washer, nut and tighten. Once satisfied that all is well, bend one of the tabs, reconnect the prop shaft and test.
Note: the OXKB is lubricated by the engine oil so check the level.
with the prop shaft pushed back there may be some water leaking from the key way run out. You should only need to pull the shaft forward a little to stop the leak. Tie off the shaft in the forward position if you are going to be away for a while.

Hope this helps