On Friday, January 25, 2019 at 9:06:26 PM UTC-6, wrote:
Easy answer is to take a 10mm open-end wrench, then grind it down until it will slip in there. Probably only get 1/8th turn per stroke!
JJ

Yes you will need to do what JJ said. Took me 6 trips to the grinder to get the wrench ground down enough and even then it was only about 1/8th turn per stroke.

Also had to do the same to a socket to get the rudder nut off.

Tony