27'semi displacement kicker size

Hello all,

have been pondering many repower options for my Selcruiser 27'. Possibly major project conversion inboard to outboard but I am getting the feeling that I will likely just repower the single diesel inboard. Paranoid about wanting a spare engine but also thought that it would be good if I can run the boat on the rivers sometimes with just the outboard. Also want to use it as a parking engine (cos I am crap at reversing up the boat on the rudder). I would want it to be on a sort of cantilever bracket so I could lift it out of the water and put a cover on when the main is running.
Garelick do a really good bracket that seems ideal but does anyone know of a supplier in Europe of Garelick stuff or a similiar mount.
The boat is semi displacement 27' and rated at 6 ton (don't think it will be that as I hope the new engine will be lighter and will strip out some of the weighty cosmetic stuff during my interior rebuild. I thought that 25 hp would be all I need as a get you home engine when we go coastal. Maybe not even that. Any more and it would weigh too much to do anything rather than tilt out of the way.
So what sort of power do you think I would need??

regards arthor