i have found alot depends on the make of the engine we have several brands/ hps
we have one 30hp (can not remember brand of top of head) that is more powerfull than the 36hps minnkotas,
personally dont rate shakespears they seem to have more problems and no where as powerfull as other engines of same size
our engines are used daily and have few problems with them,
battery wise we use lesure batteries mainly 115 amp, obviously the higher the amp the longer they last plus the stronger the engine the quicker the battery flattens.
if you want to have a look at ours and try the differant sizes/brands pop over and i will get them all out for you to look at
andrew