M20 Output Coupling

[Capt Chad]

So this is the coupling on my output shaft that bolts to the shaft coupler. As you can see there is a pretty good sized crack running down the length of it. You can only find it by dumb luck when the transmission stops with it indexed up and facing the centerline of the boat. We would have never found it except the transmission was loosing about 2 quarts every 10 or 15 hours of run time. It is slinging out of the seal for the output shaft.

Does anyone have a clue where to find this part? Allison M20L

Has anyone seen one crack like this? We just had both shafts out of the boat when it was hauled last spring. They did not see the crack then. I haven't hit anything.

 

[SKYCHENEY]

I replaced the output shaft seal on mine a few years ago. I can't tell on the photo but it looks like the seal is pushing out from the trans and that is where the crack is. Not sure without a photo that is not so closeup. I ordered my seal from Acadian Marine. They have all of the Allison parts.

 

[Capt Chad]

I've not seen it yet. Mechanic says the part with the crack is part of the transmission coupler and that the crack goes all the way to where it bolts to the shaft coupler.

 

[Boatsb]

Your mechanic should be able to get a BOM and source the parts.

 

[SKYCHENEY]

Could be. Just take the coupler off of the trans and then pull the back cover and the seal comes out fairly easily with a slide hammer puller. Once the coupler is off, then you can clean it up and get a better look at it.

 

[Capt Chad]

So what holds that coupler to the output shaft a bolt? Any idea what torque? I'm trying to figure out how far back I need to push the prop shaft and its coupler. Did you do yours in the water?

 

[SKYCHENEY]

So what holds that coupler to the output shaft a bolt? Any idea what torque? I'm trying to figure out how far back I need to push the prop shaft and its coupler. Did you do yours in the water?

Yes, there is a nut in the center. Split the coupling and push the shaft back a little then remove the nut and position a socket on the end of the output shaft and tighten the two couplings back together. That will pull the trans coupling off of the shaft. I can't remember the torque for that nut but Acadian will tell you what it is.


Here is the contact info:


Brian Lemmon (Vice President)

Acadian Marine Transmission, inc.

217 Burgess Dr.

Broussard, LA. 70518

CELL # (337) 552-6285

PH # (337) 837-3636

FAX # (337) 837-3633

email: blemmon@acadianmarinetransmission.com

WEB: www.acadianmarinetransmission.com

 

[Capt Chad]

The coupler is definitely destroyed.

Did you break that nut loose with a breaker bar or did you have to make enough space to get an impact in there?

Thanks

 

[jmooney]

I have seen yard workers pound the shaft at the props with large hammers in order to jar the prop loose from the shaft . I wonder if this was the start of this problem.

 

[Capt Chad]

Sky Chenney, Thank You.

That was the hook up. Brian is extremely knowledgeable and had everything I will need.

He's also sending me the parts breakdown. So if anyone on here needs it message me and I will get it to you.

He also told me that he's never seen that flange crack like that. There are too many items on either side of it that are made from a lot less steel that would absorb an impact or shock before it got to it .

 

[SKYCHENEY]

The nut came off with a breaker bar.