Big Twin lower Franken-unit damage

[baytonemus]

The lower unit on my '63 Big Twin 40 appears to have been originally from an Evinrude (blue paint underneath), then put onto a Johnson (white paint on top), then eventually onto this Evinrude. It does appear to be a fit, however, and for the most part corresponds to what's in my parts catalog. The service manual says there are 16 rollers in the lower pinion bearing and I took 17 out of mine, but who's counting?

I'd appreciate some help evaluating the seriousness of the damage I'm seeing.

Propeller shaft oil seal housing retainer



This must have gotten twisted on the shaft at some point and has been planed down at an angle. However, nothing rides against this side of the retainer so it seems mostly cosmetic. I'd prefer to save the $40+ it would cost to replace this. I will if necessary, though.

Drive shaft grooves



These grooves appear to correspond to the top and bottom of the upper drive shaft to gear case bearing and are only on one side. I'm not sure what would cause this. Maybe that upper bearing is bad? The drive shaft does not appear to be bent.

Leaky gear case



My assessment of this is mostly based on the fact that the outside of the bottom portion of the gear case - below the seam where the upper and lower sections are screwed together - was greasy. (The photos do not show this.) I can also see a few remnants of a couple of different types of silicone near that seam. It seems to me like part of the problem might be that the screw holes are inside the gear case seal groove. So, unless the two parts of the case are perfectly flat (they're probably not anymore) OR the bottom of those screw heads really seat up tightly (they probably don't - everything is pretty dinged up), I could easily see where lube could leak through the screw holes. Would it be too risky to have the surfaces planed?

I welcome your collective wisdom! Thanks.

 

[F_R]

Re: Big Twin lower Franken-unit damage

1. The portion of the seal retainer serves only to keep the seal from blowing out.

2. The bearing is probably shot. More serious, the gearcase is probably bent. Give it enough time and the shaft will break. Take the case to a machine shop and have them check the parallelism between the top and bottom surfaces. They will put it on a granite plate and use a height gauge to do that. No matter what, that shaft is toast.

3. DO NOT remove metal from the case or skeg. The bored cavity won't be round any more if you do. Clean it up and remove any high dings, and seal it properly. "Properly" means use Scotchgrip #847 sealer and put it around the screw holes. Put some under the screw heads too, if you feel it really needs it. Sock the screws in tight with a hammer impact screwdriver.

 

[baytonemus]

Re: Big Twin lower Franken-unit damage

Thanks again, F_R. Tonight I did find in the gear case reassembly portion of the service manual instructions about using Sealer 1000 on the groove and another type on the screws. Even though the motor has not been running since I've owned it, I'm pretty sure that I had that gear case open at one point a few years back. I didn't have the service manual at the time, so I'm quite sure that no sealant was used during reassembly. This 3m 847 presumably is the appropriate substitute for the sealant mentioned above.

Disappointed to hear about the drive shaft...

Another factor here is that while I was cleaning up the lower portion of the gear case (is that the "skeg"?) tonight, I found a small crack in the right rear. I tried to repair it using HTS-2000 brazing rods but my MAPP gas torch couldn't get the material hot enough.

I'm wondering now at what point I should simply abandon this lower unit and try to find another one? I'm not sure what that might run me or what I might end up paying to fix these individual pieces.

 

[jimdd810]

Re: Big Twin lower Franken-unit damage

these lower units are cast as one peice then seperated at the facotry and machined for together. I would be looking for another lower unit and drive shaft. The one you have looks like its been leaking for awhile. The silicone your talking about tells me that someone found it leaking and tried to seal it up with it. As you may know that isnt going to work. you might find a different lower unit or doner motor for a resonable price instead of replacing every thing and then trying to weld it. Ive never personnally seen a lower unit thats been welded (except for the skeg) thats been able to be resealed. to much warpage. Just my 2 cents.