Hey Hoop,
Like roop said. The P79 is like an open bottom cup and the bottom is cut at an angle. It even has numbers molded into it cooresponding to your boats deadrise. You twist it til your deadrise is pointing forward which makes the ducer point straight down. Fill it with mineral oil, screw on the ducer and your ready to go.
I don't know how this pic will come out , but lets see:
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Bill