I repowered my 18 footer last year and went thru the same process of trying to decide whether it was going to be four stroke or two stroke . It finally came down to many things, weght ! weight! weight! weight! The kicker was a no brainer, its got to be a four stroke for trolling. It weighs 125#s . A new two stroke weighed 40 - 60 #s less than the old motor and a new four stroke in the same HP catagory was approximatly 100#s more. went with the two stroke. Maybe in a couple of years the mfgs. will get the weight down on the four strokes but I wouldnt count on it. In the mean time I love my optimax