Well thanks everyone for your opinions so far. I realise there is a lot to consider, including the perennial argument as to weather
or not there is anything to be gained by leaving the pump on standby when not on board and thereby having part of the electrics live while unattended and if a large leak did occur then the batteries could likely run flat in any case and the boat eventually sink. Kind of damned if you do, dammed if you don't I guess... The boat already has a large manual pump that I have never had to use, as the bilge
always remains bone dry. I feel the likelihood of her developing a major leak when parked up is slim but you never know...
Obviously mid transom quite high up would be the best outlet position with perhaps an anti siphon loop. Thanks for that advice.