They put on the side for motor clearance! If thats what you want. I put my electric motor on the side and use a center mount. In fast water when anchored a side mount will tend to twist the boat, consequently the boat will get pushed down stream immediatly because the chine is now plowing. A center pull will usaually keep the boat strait and it will actually sit for a few seconds before it starts moving down stream, giving you time to grab the oars and get the boat in control. assuming its a Willie or something designed comparably. This is particularly important when you have a slot you want to fish on anchor and the water is very fast your anchored in and directly below it is a hazard or tight fit were a twisted boat can mean the difference of making it or slamming into it sideways! Some boats are tubs and wont hold for anything! One key factor is to make sure your boat is set up properly. You dont want the back being pushed form the current. Ive seen some mass produced boats "A" that drag even with 2 guys in it. My Willie wont drag with 4! It may have been that the boat was set up wrong but Ive had 4 boats now and nothing Ive ever rowed acts like my Willie.

Bob D