I have an oarmaster II in a Kittery Skiff.  I've rowed an Annapolis Wherry but I didn't pay attention to the way the base of the rowing unit mounted on the bottom.  The Oarmaster is a very good unit which I am completely satisfied with.  The important thing is to measure the height of the out riggers to make sure they clear the gunnels.  Otherwise you will have to raise the whole unit by installing risers on the bottom of your boat or attach them to the bottom of the units frame.  Happy Adapting!