This is my first boat, and i've never set one up before, so I have a question about what gas motor i'll need when i get one. The boat is a Grumman 14' V bottom. I have an old Min Kota 65C electric as the sole motor (aside from my passenger and paddles). Assuming i'm measuring right ( bottom center of hull to top of transom) it looks to be 16.5" transom height. Would I use a 15" short shaft outboard or do I need to look for a 20" long shaft? Does the prop need to be lower than the bottom of the hull to get good water flow through it? I assume that's why they make tunnel hull boats, to provide a clear shot to the prop without interference from the hull.