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View Full Version : Shaft coupler nut (transmission side) came off today


macattack
08-06-2011, 09:03 PM
Searched 115 threads on shaft couplers, but could not find one that discusses the transmission side of the coupler nut coming off.

Ref a 2005 MC PS197 TT, ZF Hurth transmission, 620 hrs...while setting up our slalom course this morning, put the boat in reverse and heard a loud metal clunk. Checked underwater and found the prop/shaft had slid out and hit the rudder. Opened up the engine box and saw the splined shaft sticking out of the back of the transmission and oil streaming out into the bilge...not a good feeling:(

Once home, took the shaft coupler apart and found a large 2" diameter, 1/2" thick specialty type nylon nut laying loose inside. Now I am feeling a little better since it doesn't appear to be as bad as I initially thought:) except for the 2 hrs it took to clean up all the oil:(

A few questions:
- Unfortunately, this nut requires a special socket...it goes by many names accordingly to a Google search...hub socket, hub spanner nut socket, spindle nut socket, front hub socket, etc. Obviously, there is a specific "auto" use for this socket, hence one size for that application. I checked at a couple of different auto parts store and their limited spindle nut sockets are too large. Anyone know where to get this specific socket/size for this nut???

- Are there any torque recommendations when putting this nut back on??

- Any thoughts on how to prevent it from backing off again??

- What reoccurring checks can we perform to "catch" this before it happens again...hopefully something easier than taking the couplers apart every so often to check both nuts are still tight?

- Has MC issued TSBs on this subject?

It is mind boggling this can even happen (design wise), but apparently from reading the other "coupler" threads it seems this happens often on the prop side coupler nut.

Thanks for any thoughts or insights, mac

langedp
08-06-2011, 10:13 PM
I had this happen to my X-Star last season. Although it's a v-drive, it was the same issue. The large nut on the transmission side spun off in reverse. The shaft then shifted backward until it lost contact with the coupler splines. I ended up getting towed in.

Skidim had the nut. Talked to a local dealer and was told to torque it down as tight as I could get it. One season later and it's still holding.

See this thread...

http://www.mastercraft.com/teamtalk/showpost.php?p=692217&postcount=3

macattack
08-07-2011, 07:49 AM
I had this happen to my X-Star last season. Although it's a v-drive, it was the same issue. The large nut on the transmission side spun off in reverse. The shaft then shifted backward until it lost contact with the coupler splines. I ended up getting towed in.

Skidim had the nut. Talked to a local dealer and was told to torque it down as tight as I could get it. One season later and it's still holding.

See this thread...

http://www.mastercraft.com/teamtalk/showpost.php?p=692217&postcount=3

Did your transmission nut look like mine; if so, where did you find/buy the socket to use to tighten it down...tks, mac

ncsone
08-07-2011, 09:01 AM
Mac -

In your research, did you find out what the name is for that type of nut?

-Neill

langedp
08-07-2011, 10:55 AM
Did your transmission nut look like mine; if so, where did you find/buy the socket to use to tighten it down...tks, mac

No, mine is a large, more normal looking nut with nylon insert. I called Discount Inboard Marine and asked. He knew what it was and had them in stock. They probably have yours as well as the socket to fit.

ted shred
08-07-2011, 12:42 PM
Be sure to clean it real good and put some blue loctite on it before you tighten it down.

FrankSchwab
08-07-2011, 04:27 PM
I've had to deal with those (no idea what the real name is) on motorcycles in the past.

Being a cheap bastard, I made my own tool. Take a socket where the outside diameter matches the outside diameter of the nut, and cut slots out of the socket leaving the necessary tangs to engage the nut using a Dremel or other cutting wheel. The Swap Meet is always a good place to find appropriate size sockets for $1, or you can go to your favorite hardware store and spend $10 on the right size (or, as I found, the appropriate size socket was one that I had never used, so never replaced it).

macattack
08-07-2011, 04:40 PM
Mac -

In your research, did you find out what the name is for that type of nut?

-Neill

Hey Neill, I'm narrowing down the name of the socket... a 4 lug outer (vs inner) spindle nut socket...I have not seen this exact nut in any of my searches (to include SKIDIM), but I would assume the name would be similiar to the socket.

Pretty frustrating to say the least...dead in the water, because I can't find the right socket to put this nut back on!! Will be even more frustrating to make a 4 hr round trip to the dealer...mac

macattack
08-07-2011, 04:44 PM
I've had to deal with those (no idea what the real name is) on motorcycles in the past.

Being a cheap bastard, I made my own tool. Take a socket where the outside diameter matches the outside diameter of the nut, and cut slots out of the socket leaving the necessary tangs to engage the nut using a Dremel or other cutting wheel. The Swap Meet is always a good place to find appropriate size sockets for $1, or you can go to your favorite hardware store and spend $10 on the right size (or, as I found, the appropriate size socket was one that I had never used, so never replaced it).

Frank: This may be the best idea thus far...a lot of grinding, but better than towing the boat to the dealer...tks, mac

ncsone
08-07-2011, 04:44 PM
Look around SnapOn.com. I have seen some similar to that on their website, just not sure if it was an exact match. It will be costly, but it may be you only option.

mtajpa
08-07-2011, 04:49 PM
Frank: This may be the best idea thus far...a lot of grinding, but better than towing the boat to the dealer...tks, mac

Looked around on a couple of Hurth sites and they want 270 bucks for that socket/spanner. I'd go with Franks suggestion but I would try to use an impact socket as they are alot stronger.

ahhudgins
08-07-2011, 06:56 PM
I do CNC machine repair and I see those nuts a lot on servo motors. I have several adjustable spanner wrenches and they function the same as a regular adjustable wrench but they have two tabs for gripping two opposing slots in the nut. Your problem is that a spanner wrench won't reach inside the coupling. I agree with other responses and I believe I would have to grind down a socket unless I could find one for under $20.

Jerseydave
08-07-2011, 07:43 PM
That's a 4-pin spanner socket, also used on alot of 4WD truck hubs. You can find them through Snap-on tools, Mac tools, Matco, and also NAPA should have access to them through the OTC brand. You need to know the diameter of the socket needed as they come in different sizes. Should be under $25 through most tool dealers.

JimN
08-07-2011, 08:01 PM
IIRC, ACME has one in their catalog and it amounts to a steel bar with two studs that pass through two of the coupler holes. If a 1/4" x 1" bar had two holes drilled and tapped, with an arc ground at the center so the socket & nut can be tightened, it shouldn't cost much and would be pretty easy to make.

On the boat in the original post, there's no clearance problem WRT the two halves of the coupler- some boats have almost no room to fit a short socket between the shaft on the transmission and the nut on the shaft, so the only special tool needed is for holding the coupler on the transmission in place while the nut is tightened. On a Prostar, it's sometimes necessary to cut a socket off so it's short enough to fit and grind a pair of flats on it so an open-end wrench will fit- that's what I did. The cut off socket could be welded onto a flat piece of bar stock, too.

Moosecrackers
08-07-2011, 08:50 PM
In my history, these are tightened with a Spindle Nut Wrench. Grainger sells them. They come in different sizes so you'd have to match it to the size of the spindle nut.

FrankSchwab
08-07-2011, 08:59 PM
Googling "Spindle Nut Wrench" and "Spanner Socket" both appear to return useful results, with "Spindle nut wrench" perhaps having the edge in readily-available tools.

Guess I learned something today.

/frank

macattack
08-16-2011, 07:23 PM
Just a follow-up...lots of great inputs on where I could find a spindle/spanner nut socket, but no luck in finding the correct size. So, I bought a $7.50 1 1/2" socket from Auto Zone and took it to a local machine shop to have one made for $45...totally impressed by the professional results! I also made a "tool" to help tighten the nut back on.

macattack
08-16-2011, 07:28 PM
Now, for the "not so good' news...pulling up a skier, I am hearing a slight "clunk" noise; this happened on every pullup...count 1001, clunk. No noise pulling the skier through the course and could only duplicate it once without a skier. Took the shaft couplers apart again and checked the tightness of both nuts and also checked the prop nut...every nut was tight. Any thoughts? tks, mac

Table Rocker
08-16-2011, 07:30 PM
Well done!

mtajpa
08-16-2011, 07:37 PM
Awesome Job on the socket. Maybe rent it out to whoever needs it next and you'll make out in the long run.

As far as the clunk I would make sure your prop is tight also not sure if yours is tapered or splined but that is where I would start first. How did the alignment match back up?

macattack
08-16-2011, 09:21 PM
Awesome Job on the socket. Maybe rent it out to whoever needs it next and you'll make out in the long run.

As far as the clunk I would make sure your prop is tight also not sure if yours is tapered or splined but that is where I would start first. How did the alignment match back up?

Shaft is splined and the prop nut is tight, but the shaft alignment is off....015" at the 0600 and 0900 clock positions. Obviously, I need to fix this, but not sure this is making the clunk noise?

FrankSchwab
08-17-2011, 12:28 AM
I can't see the .015" leading to a clunk sound.

Try checking the motor mounts or the transmission mounts. Maybe they've gotten loose and the engine is rocking up and then setting back down with a "clunk".

macattack
08-20-2011, 12:24 PM
Happy ending...water tested/4 sets in the slalom course this morning; no more clunking noise, the boat runs great! I believe the "clunk" came from the two 30lb mushroom anchors that are stored under the observer seat that help balance the boat when course skiing w/only a driver. It appears one of them was rolling into the other one on acceleration and then rolling back on deceleration. They are now bungie corded together!

I did realign my engine and found the back two bottom motor mount nuts somewhat loose, but not sure they were loose enough to allow the engine to raise up and lower with a clunk. Somewhat loose is relative to how much you compress the 1/2" thick rubber bushing btwn the nut and mount??

Anyway, had great results with the alignment...about .0015" all the way around the coupler. The prop will now "spin" about 3/4s of a revolution where before I could move it around with a little pressure, but not spin it. Thanks for the feedback on this one...mac