Jabberwocky to GTR :- Rudder Repairs

The internet was a fantastic resource which was always there to help with the rebuild process, from sourcing supplies to researching new skills there was almost nothing that could not be solved with a simple search. As with everything there is always an exception to the rule, no matter how hard we searched we could not find any detail on how to replace the rudder bearing on a Mumm 36. So while this post is a simple one it should solve the problem for the next team to take on a Mumm 36 rebuild.

So how do you replace the the rudder bearings on a Mumm 36 ?

Click the play button below to watch the video or read on to find out how to do it.


The first part of the process was quite easy, undoing all the tiller mounts gives you easy assess to the top bearing. With a little bit of pressure the top bearing was remove,d as it was above the waterline it was wasn't in bad condition considering how much movement there was in the shaft and that it was 20 years old.

Now for the tricky part, how to get at the bottom bearing :-

• After trying to unscrew the bottom bracket from every angle it became apparent that it was fixed in and would not unscrew.
• At this point we followed my dads approach to DIY, if a first you don't succeed get a bigger hammer. We started with a small hammer and some wooden blocks tapping away from the top of the shaft. Still no movement.
• The hammer got bigger until we ended up with a 15 pound sledge hammer with a custom made wood cover to protect the top of the shaft as we swung ever harder.

Still no movement !

It was at his point a new approach was needed, with cutting blade in hand an incision was made round the metal brackets under the boat. We were a little worried at first but as we completed the circular cut it became obvious that this was the only way it was ever coming out. The bottom mounts were epoxied into the hull, a neat circle around the bottom bracket and it easily slipped out.

Once out we hoped that like the top bearing we could clean it up replace some ball bearing before putting it back in. It soon became obvious that would not be the case, with the bottom bearing under the water line it was heavily corroded, so much so we could not even get it off the shaft. We had to go a little easier with this part of the removal process as we wanted try and reuse it, so the sledge hammer was not an option at this point. 

As custom jack mount was built and after applying nearly 5 tonnes of pressure per square inch the bearing was finally persuaded to leave the shaft that it had become so attached too.

The clean up crew went to work doing a fantastic job tidying up the old bearing, while the results were amazing sadly it was beyond repair, there would still be too much movement due to all the wholes created through years of corrosion. 

Sadly the bottom bearing became the first item that could not be restored and a new one would have to be purchased. A quick search on the internet created the next issue. Harken no longer produced the bearings, luckily it did not take too long to find out that Jeta had taken over production post Harken stopping. While the bearing was quite different in design it was made to the same specification and would be as good as a like for like replacement. 

Once the new bearing arrived things went back together relatively easily, with only a few adjustments required to the shaft height to ensure the correct alignment with the new bottom bearing. After all the work trying to get it out it was great to know that when we epoxied it back into place, that the new design allowed for easy removal for future cleaning as only the aluminium holder is now fixed.

If we can clean it regularly is should last at at least 30 years before the next replacement is required.

Watch the whole story from the beginning by clicking the play button below.