I thought it was used to describe the use of an engine whilst under sail, namely 'plonking' whereas the offender himself then becomes known as a 'plonker'. It has been known to cause broken engine mounts I believe? /forums/images/icons/smile.gif
<hr width=100% size=1><font size=1>Sermons from my pulpit are with tongue firmly in cheek and come with no warranty!</font size=1>