I have a standard shaft 3.3 hp Mariner and have just bought an outboard bracket for Boats & Bits (expensive but far cheaper than anything I could get made locally) I’m very pleased with the quality and impressed at the very quick delivery.
They give some guidance for fitting the bracket, 400mm from the rudder centre line and the top of the base plate 130mm down from top of transome. This places the top of the actual bracket approx 15mm above the top of the transome.
In an article in Wayfarer New Summer 2001 the bracket was positioned 90mm down form top of transome. The writer then found that his 2HP Honda was not deep enough in the water, he then changed to a long shaft version.
As usual Matt your comments make sense, with a dinghies moveable ballast you just adjust trim to suit. I’m just off to the garage to start cutting holes and will see how the positioning works out with motor and rudder in place.