Backing up from the dock last fall taking it out the pontoon for the winter and hit a rock and motor quit. Now it just has a clunk noise when turning key. I replaced the fuse I found in motor, new starter battery with no change. I was told crankshaft may have broken which is a possibility, but wouldnt it turn over and start at least? Shift handle is in nuetral when starting.  Anything I should look at before I bring it in for service?