Re: putting 3 wire trim system on motor set up for 2 wire.
do you mean putting 3w trim system on a 2w gas outboard engine? Or do you mean putting 3w trim hydraulics on a 2w trim motor?
If you mean putting a 3w trim system on a physically compatible engine that has a 2w trim harness then it is easy. Your trim relays have five connections. The one in middle should be a heavy black wire connected to post 87a. Disconnect that wire on both relays. Connect trim motor ground to engine block ground. That's it. Your 3w motor will run off your 2w relays.