It's true that a small engine will struggle to make a boat go anywhere near well in a larger sea however I work on a self sufficiency basis, aux = 15hp
oars 4 vhfs flares epirb 2x gps etc etc the aim is get myself out of trouble if I can.
on the 1 occasion we lost the main engine it was in the middle of a busy shipping lane.
coastguard called we trundled out of the way on a 3.3 merc. we then ran 13 miles back without problem sea start would not have helped we would have been toast
, so I do feel it is always worth having an aux.
The other I noted was that most of the time the prevailing conditions are good on the days we go out and so most of the time the aux is fine.
definately get one