Well, I've just discovered my boat has the same problem as Keith encountered.  I had thought a leak in that area (which I briefly had this past summer) was from an aged shaft log hose, so I put it down a hose replacement on this winter's project list; but now that I've managed to withdraw the prop shaft, I discovered that a misalignment at some point eroded away the bottom of the shaft log tube itself to paper thin and in some spots not-existent  -- see photo attached. Looks like the only thing keeping the ocean out was the pressure of the hose against the hull.
   I haven't found a write-up on this page of how to install the replacement  (Catalina Direct does sell the shaft tube replacement for around $50); if anyone has I'd love to hear how it was done.  (I don't think attempting to repair the existing tube would be a good idea).
  There was mention earlier in this thread about a Mainsheet technical article about this, but I haven't found it in the archives for the 36; perhaps it was a different size Catalina.  Anyone know when that article was, and how one can access archived tech articles for other Catalinas?
   By the way, I would imagine that the incidence of this problem might be more widespread than folks realize --- but one might not have much warning of it (since inspecting the condition of the tube is essentially impossible without removing the hose, which means removing the shaft, which means removing the flange, prop, and cutlass bearing).
 

[quote=MitchMan406] ...I would be hesitant to try and remove the entire shaft log and glass in a new one.

First replace the motor mounts. Most people -like myself - don't realize that the root of the problem is improper shaft alignment.  Brought on by poor engine mount tuning or in failure or fatigue in the rubber portion of the engine mounts themselves.

I opted to repair the existing tube by building up the bottom of the shaft-log tube with small  pieces of glass and graduating up to larger pieces, glassed into the interior of the tube....
 [/quote]
    Thanks so much -- these sorts of exchanges is what makes this Association so valuable (one of the reasons why we chose this model boat!).
    Actually, one of the very first things we did when we bought our boat 5 years back was replace the mounts (per the survey recommendation); thus I suspect that this was damage from past mis-alignment by a prior owner at some point in our boat's history.   Since few of us are original owners, we really have no way of knowing what lurks in that area -- unless we proactively take the whole thing apart (no small task!).  I only discovered a leak there when I apparently nudged the hose a little while repacking the stuffing box.  I now realize there was no "there" there! 
   Anyway, its good to know that it can be repaired without replacing the entire tube -- which seemed to me to bring a whole new set of challenges.
  

[quote=JSM]Hello All, After untold hours of searching the web I'm extremely relieved to find this post. I recently purchased an 87 Ericson 34 that we had to have hauled two days after taking ownership due to this same problem.
I will be attempting to re-glass the tube this weekend and would greatly appreciate any guidance from those who have done this repair as to exactly what materials you used and how the repair held up for you.
In addition to repairing the tube I will be installing new motor mounts , a new shaft and coupling as well as a PSS dripless shaft seal.
Thanks
John and Susanne in Chicago.[/quote]
My deepest sympathies!  Obviously, a different boat may have a different set of obstacles, but I can tell you that the repair I did 2 years ago seems to be holding up just fine.  My prior posts above give some of the procedures I used.  Seth Mitchell ("Mitchman") did a very nice writeup on this procedure, which I used as guidance, if you PM me or Email me I'll forward it to you (he also was quite helpful in discussing this with me over the phone). 

My hindsight observations: In removing the flange from the shaft, DO NOT -- as I did -- attempt to remove the coupling flange from the end of prop shaft via the technique of inserting a socket between the flange and the transmission coupling and using long screws gradually tightened to press it off.  Here's why
-  First of all, it took many, many hours for me to do this, working in a confined area;
- Secondly, you run the risk of bending the fingers on the transmission end of the coupling, which another C36 member recently experienced when a yard mechanic did just that, requiring the purchase of a replacement transmission (I luckily escaped that disaster, whew!), and
- Third, you'll want to make life easier for yourself (particularly if you are going the PSS route and will have to remove the shaft every 6 years to replace it) by buying a split coupling to replace it anyway (Buck Algonquin).  So you might as well go the quicker route of using a grinder to cut a notch in the old coupling flange to remove it -- there's a Youtube of someone doing this out there that I saw (again, in hindsight).  And anyway, you'll need to bring the shaft and new coupling to a prop shop to get it machined to fit square to make sure the prop is trued, and the old coupling would probably not fit properly.  See Mainesail's excellent writeup on this at http://www.pbase.com/mainecruising/new_shaft
   Alternatively, Catalina Direct has a tool for removing the flange (http://www.catalinadirect.com/index.cfm/product/3613_844/coupler-puller-yanmar--universal-diesel.cfm) for $45;

  Since you, JSM, are planning to get a new shaft and coupling anyway, you can just cut the old shaft, but I pass along the above observations for others who may want to reuse the existing shaft (as I did).

Good luck.