hi guys this is my first post,having trouble with my sea nyphm its 17ft the one that the engine sits in a well in the boat,just changed outboards from a jhonston 25 horse two stroke,to a honda 15 horse four stroke,and gave it its first run yesterday problem is was taking in a lot of water at the back end when i tryed to gain power it was as if it was digging in everytime i tryed to give it throttle is this a problem any of you guys have knolledge of,is it the propeller?same size of longshaft any help or advice greatly apprieciated