I just purchased a 2011 16 ft Smokercraft with 50hp 4stroke Mercury outboard. The throttle on the control box doesn't seem to incrementally accelerate as it should. The engine hardly revs up with first inch or two of moving forward the throttle and then it suddenly kicks in with a lurch. This is especially noticeable in reverse. Extremely frustrating in a relatively "new" boat. Thanks for any help!