Please note this is just my honest opinion, if you are going with a 4 stroke go with a 175/200 if an Etec 150/200 will be perfect. If using 4 stroke consider a hydraulic jack plate to keep the motor up when trolling or during a heavy chop or rough seas.
My thought process is you will want to keep the engine trimmed up high preventing backwash up the exhaust ports from it sitting low in the water..
I am currently running a 87 140 v4 20" dry weight is 370 LBS lightest 2 stroke in its class yet she squats pretty low...Go to
www.boats.net and compare the weight numbers on 4 strokes best I have seen is the Honda's and Suzuki ....