Hi, just going same process although on mark 2. Not completed job yet, however this may help. check out bracket that fits in tapered shoe from boats n’ bits in Norfolk. Not cheap, just over £100 plus shipping, but a seriously secure piece of engineering leaving minimum weight permanently attached. Good quality. I have a false grp wall in the locker that was easily removed. Mine was just glass taped to a block of polystyrene fitted behind it in the rear third of the locker. I believe some boats either don’t have this at all, or have a wall that may be partially glassed in. The polysterene has now been cut out on the port side and preserved for refitting later. Doesn’t have to be that tidy a job – It will not be seen again once restored and will be just as bouyany if the tank is ever holed. Port side seems to be the recommendation for right handers to get the outboard handle in the right place for the common majority. Then a drilling sealing and bolting operation is required – Sikaflex for example for sealing. Positioning info is given with the above product – centre line of bracket 400mm from centre of boat, and top of bracket about 130mm below transom top. Other types of bracket will doubtless be different measurements. These measurements are stated as just a basic starting point and people are reminded about checking the arc of the rudder blade and any possible fouling of the engine or handle, particularly when tilted up. The consensus seems the be to offer up the whole shebang before drilling holes. Motor shafts are different lengths, etc. ON chooice of brackets, I didn’t really want to pay that much but didn’t feel the sprung lifting type were suitable although about half the price. Didn’t want such a big thing bolted to the boat all the time. I have seen a less well engineered, but doubtless effective bracket with a plate shoe rather than the substantial alloy casting of the above, but I haven’t been able to find a source. Now I’ve parted with the cash, I’m happy and impressed with the quality.
Happy drilling – just measure many times first!