Gear Oil in UJoint Bellows

bbook83

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Nov 6, 2004
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I pulled the drive on my 1974 140 out drive and discovered gear oil in the bellows, as shown in the photo. I assume it is from a failed gear end yoke seal. Is that a realistic repair for a DIY guy? I have access to the required spanned wrench, but am concerned that I could mess up the gears if not properly pre-set.

This won’t set well with the professionals here, but I am considering just monitoring the gear oil level closely, cleaning it out of the bellows periodically, and living with it, as this boat is a second boat for the family and gets only 10 hours or so of use per year. Any thoughts?
 

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Grub54891

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Fix it. Low gear oil blows the upper gearcase. There should be a video in the stickies at the top of the forums.
 

nola mike

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Not too difficult, especially if you don't need to set rolling torque on the bearings. Not sure which drive you have. Either way it's definitive doable. You just need to make sure that all the shims you take out go back in and set the bearing preload correctly.
 

Bt Doctur

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If you have an original drive that never had new gears installed a seal replacement is a snap. you will need the spanner for the castle nut
With that attitude I see a new drive in your future
 

bbook83

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I appreciate the candid responses. You have given me the confidence to give the seal replacement job a try. I have owned the boat since new, and recall the upper gears being replaced many years ago. Doc, how will that change the job?
 

bbook83

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I appreciate the candid responses. You have given me the confidence to give the seal replacement job a try. I have owned the boat since new, and recall the upper gears being replaced many years ago. Doc, how will that change the job?
 

bbook83

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Thanks for the candid replies. I will give it a try. I have owned the boat since new. It had upper gears replaced many years ago. Doc, how does that change the job?
 

bbook83

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I started a thread on this, but my response is sitting under moderator review. However, someone did manage to get a post hijack question in. I will proceed with the seal repair. The unit has had upper gears repaired before. How will that change the job?
 

Bt Doctur

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With a GEN II most likely for the carrier but not for the driveshaft seals
 

bbook83

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Mine is pre-alpha, so hopefully, I will be ok. Thanks for the help.
 

bbook83

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I split the drive and replaced the water pump. Now, as shown in the picture, I am trying to use a spanner wrench to get at the seal in the upper. I don’t have an outdrive stand and am not able to get the unit solid enough in the work mate stand shown to get good leverage on the wrench. It might be better if I put the lower and upper back together, but I’m still not sure it will be secure enough. Any suggestions?
 

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Scott06

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Yes I think better together. But I think you want to make a similar fixture to attach it to the workbench or something less spindly than the portable workbench.
try some heat on the outside of the housing where the nut goes in . These can be difficult to remove on older drives. Worst case drill it out with small drill bits and break it inward with a chisel. What year is that drive ?looks very clean but it’s been a while since I’ve seen an mc1with the hook on top of it.
 

bbook83

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It is a 1974 140, I believe called a 1/R drive. I made one last effort last night with PB Blaster and tapping the wrench with a hammer and it broke loose. I really only want to replace the seal on the horizontal input shaft. Do I have to remove the cap and the vertical gears?
 

Scott06

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That’s in really good shape for a 1974. merc had I think 14 drives prior to the R/MR/ alpha one I think So hard to tell but ther is a lot of interchangeability from the mc1 thru alpha gen 1 (1990)

I think you will need to remove the cap to make sure the shims etc go in corrct when reinstalling the input shaft and drive gear. also since on this drive with no reservoir when you loose oil into the bellows the upper gears and top bearing can run dry they may be worth a look as well.

You may end up with a groove And or corrosion in the yoke That the seal you are replacing rides on. I think you can replace the yoke, put a spedi sleeve on it , or sand off any corrosion and install the seal .040” deeper to ride on a clean portion of the yoke.

you may want to check out the lower seal in the upper on the vertical drive shaft as it is likely worn as well or close to it. Did you do a pressure test to see where it was leaking ?just assuming if oil was in The bellows Other seals may not be holding either.
 

bbook83

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That’s in really good shape for a 1974. merc had I think 14 drives prior to the R/MR/ alpha one I think So hard to tell but ther is a lot of interchangeability from the mc1 thru alpha gen 1 (1990)

I think you will need to remove the cap to make sure the shims etc go in corrct when reinstalling the input shaft and drive gear. also since on this drive with no reservoir when you loose oil into the bellows the upper gears and top bearing can run dry they may be worth a look as well.

You may end up with a groove And or corrosion in the yoke That the seal you are replacing rides on. I think you can replace the yoke, put a spedi sleeve on it , or sand off any corrosion and install the seal .040” deeper to ride on a clean portion of the yoke.

you may want to check out the lower seal in the upper on the vertical drive shaft as it is likely worn as well or close to it. Did you do a pressure test to see where it was leaking ?just assuming if oil was in The bellows Other seals may not be holding either.
 

bbook83

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Thanks for the help Scott. The yoke assembly did not come out easily, but here it is on the the bench with a shot of the driven gear as well. Both look good to me, so I don’t think I have damage from the leak. There were two shims, which I have left as they were in the housing. I have only short opportunities to work on it, but I now have the seal kit, so I will disassemble and install tomorrow. I can see what you mean about being able to see down from the top during re assembly, so I will remove the cap before I do it.
 

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bbook83

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Thanks for the help Scott. The yoke assembly did not come out easily, but here it is on the the bench with a shot of the driven gear as well. Both look good to me, so I don’t think I have damage from the leak. There were two shims, which I have left as they were in the housing. I have only short opportunities to work on it, but I now have the seal kit, so I will disassemble tomorrow. I can see what you mean about being able to see down from the top during re assembly, so I will remove the cap before I do it.
 
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