Centerboard was raised. We were motoring slowly through the Swinomish channel in the San Juan's on a very low tide (had completed about 10 3/4 miles of the 11 mile length :-(). I have gone through this channel before, but if I do this again on a low tide I think I would try to pull the rudder up as much as I could. The one bit of good news was that we were coming home and the weather was calm enough we could get the rudder off the remaining Gudgeon, temporarily plug the holes and motor back to Everett (while testing our bilge pump
). Also interestingly the rudder was not hurt by whatever we hit (the steel rudder pin was bent and the rudder did get pretty gouged by the prop...)
With respect to your backing plate, I think you may have a somewhat similar dilemma to me. This feels like a "math question". For me, I have 4 1/4 inch fine threaded screws that have been screwed into a 1/4 inch aluminum backing plate. There are 3 things I don't know:
1. What is the holding strength of those 4 screws?
2. How much pressure is applied by the rudder under normal operation to that lower Gudgeon?
3. What was the holding strength of the lower gudgeon in the original design, which just used 4 bolts and washers against the hull?
The similar issue we may have is that I do not want to actually pull the backing plate through the transom (or the transom "off") if something like this was ever to happen again. Four small holes is very preferable to that (and I wondered if this was part of the original design). As an aside, at one point a couple of years ago there was a guy in Idaho that built a "flip up" rudder for the E254, and there are threads in this forum that reference that.
Finally, good to know I might be able to reach the transom. I thought if I took the door off I might be able to get through the hole and even researched moving the water tank for the guy working on it....but he was not getting through the door.....
, so we dropped that approach....