Have any of you replaced the trim limit switch/sender on an Alpha One Mercruiser? I am in the middle of the process and I have found a few choice words for the designers of the stern drive. The upper bolt that holds the wires as they enter the transom is IMPOSSIBLE to get out. There is no way to get a wrench on it and turn it. I have tried short, long, crooked, off set, flexible and crow foot 5/16 wrenches to no avail. The bolt it situated where there is not enough room for a socket. There is no way a straight open wrench can get on it and turn. I can get an short off set wrench on it but I only have about an inch of movement due to the other items in the way. Just how does a person get this **** thing off, not to mention trying to put it back on again. I understand the later model Mercruisers are easier to deal with since they only have one bolt and it is accessible.
As you have discovered, there is no good way so long as the gimbal ring is in place. And of course, the gimbal ring is also major surgery. There is an access hole/plug kit that can be installed to help remove the gimbal ring BUT, if you have some sort of bulbus protrusions on your transom, that may not work either. In addition to the kit you will need a huge pipe tap, 1 1/8 inch I believe.
Real irony here is that back in the mid 70s, MerCruiser built these transom plates with the access plugs factory installed.
Back to your problem, I think if you have a few different brands of wrenches and are possibly willing to heat and bend them you may be OK.
You are correct it is impossible. I tried to replace the unit and splice on to the old wires. Bad idea I am going to wait till the bellows starts leaking the get into it and do a major replacement of all toes thing that are Packard in there. Merc did not do us rifgt
It is best to remove the bell housing hinge pins first, but you will have to order the special socket adapter from Merc for that. Try removing the lower bolt, cut the wires off flush (as you are going to replace them anyway) and bend up a wrench to get in there, it can be done. Pull everything out and chuck it over the fence to feel better. Grab a roll of .035 mechanics wire and attach it to the free ends of the wire to feed it through the grommet hole. Have a helper on the inside pull the wires in tight to the transom while you re-install the plate and lower bolt only, leave the top one out as it is not required. Install the switches and adjust, test, and go grab a drink for a job well done.