transmission fluid leak

[BrownVette]

Hey all, just bought my first boat a month ago. Changed the packing and noticed that the carpeted cover plate had ATF on the underside of it, but no puddles in the bilge or anything. Checked the level and all was good. Took it out the following weekend and while I was pulling the tube it would cut out as if it were losing/struggling to get fuel. I changed the fuel filter and wanted to inspect the rear shaft for leaks or anything. There was a puddle of ATF and the leak is coming from the coupler itself. Is there a seal inside of the coupler that I need to change? The rear seal itself is not leaking. I've attached some pics. Thanks! 2006 Moomba Outback, direct drive

28774

28775

[z28ke]

I doubt there is a seal in there, if you take the bolts out of the coupler and move the propshaft back I’d imagine there is a nut/washer or bolt/washer that holds the yolk on the transmission output shaft.

More than likely fluid is seeping between the splines of the trans output shaft and the yolk. If you remove the nut/washer or bolt/washer and put a thin layer of rtv silicone (ultra grey has always been my go to) in there all the way around the splines, then reinstall the nut/washer or bolt/washer that should keep it from seeping out.

Keep in mind you will need to find the torque spec for the nut/washer or bolt/washer to properly tighten it (and if it calls for a particular locktite - typically red on something like that).

I’m very vague on this because my knowledge comes from automotive not marine (and I’ve never removed the yolk on a boat transmission) but the principles are typically the same.

Hope this helps....

[james yarosz]

I cant say for sure but I gotta believe where the yoke goes into the back of the transmission there has to be an oil seal.I dont know where but somewhere there has to be an exploded view of the trans and I,m sure it will show an oil seal.

[james yarosz]

http://marinetransmissions.info/uploads/73c_ddtrans.JPG Look at part #3.

[z28ke]

Part number 3 is the outer seal, op said that’s not leaking. If it’s dripping from inside the coupler then it’s gotta be from the splines I would think....

[BrownVette]

Thank you all for your replies! I too have vast automotive and maintenance knowledge which is why I am kind of puzzled. My concern is why it would all of a sudden be leaking through the splines...I would assume high levels of pressure have built up and its forcing it's way through. Also one more point...the boat has been sitting for a week and its still leaking.
Also, that is correct, the rear transmission seal is not leaking, I checked that first.
I did stop by a boat shop and he said there should be a seal.in the couplet..which would be new to me..but he also sounded very unsure of his answer which is why I turned here. I will take it apart and post pictures incase someone else runs into this.

[z28ke]

Thank you all for your replies! I too have vast automotive and maintenance knowledge which is why I am kind of puzzled. My concern is why it would all of a sudden be leaking through the splines...I would assume high levels of pressure have built up and its forcing it's way through. Also one more point...the boat has been sitting for a week and its still leaking.
Also, that is correct, the rear transmission seal is not leaking, I checked that first.
I did stop by a boat shop and he said there should be a seal.in the couplet..which would be new to me..but he also sounded very unsure of his answer which is why I turned here. I will take it apart and post pictures incase someone else runs into this.

Might as well bust out the feeler gauge and check the propshaft alignment while you are in there!

[BrownVette]

I will surely do that! I will update with pictures. I found the leak. It is leaking through the coupler part that is connected to the crank. I'm going to order a new one and go from there. Anyone know where I can get the torques specs and etc for the coupler?

[BrownVette]

So, I have pulled the output shaft coupler and the output seal on the transmission. Being that the coupler and the shaft are splined, I'm assuming I should be able to slide the coupler back on by hand, but this is not the case. Will I need a special tool to press the coupler back on? Or do I need a new coupler?

[z28ke]

So, I have pulled the output shaft coupler and the output seal on the transmission. Being that the coupler and the shaft are splined, I'm assuming I should be able to slide the coupler back on by hand, but this is not the case. Will I need a special tool to press the coupler back on? Or do I need a new coupler?


BFH??? (Big F’n Hammer)

In some applications that is how it’s done without an installer. But u can make an installer with threaded rod the same thread size as the bolt that came out and some nuts/washers and plenty of antiseize on the threads. Looks something like this:


https://ls1tech.com/forums/attachments/generation-iii-internal-engine/612837d1501332959-diy-crank-pulley-installation-tool-06ec32f0.jpg