Ran a 90/60 2 stroke merc on an 18' alumaweld flat that did the trick quite well. We had that boat loaded HEAVY several times (used it for working a research project in the snoho basin) and it still seemed to get up and go. 3-4 people absolutely no problem. We also ran a alumaweld dory (16' I think) with a 60/40 yami 4stroke pump. Big difference. I think stlhdr42 hit it on the head about the motors matching up to the boats. Some boats do great with specific motors, ie the 20' free drifter with a 115 yami 4stroke. Boat is just balanced correctly.