The puck is merely a compass, used strictly for heading information. I personally have seen them mounted just about anywhere. However, if you really really really want to get technical with it, the following is how you would do it. (unlike mag compass in a airplane, there are no compensation screws)
Take a magnetic compass and you boat to a grassy area (no metal around). place the mag compass on the ground then with a string and wooden stake, align the center line of you boat with the string pulled from magnetic north keeping the compass at least 10 feet from your boat. Now, take the compass and set it various places on your boat. The spot where the compass remains aligned with the center line and does not deviate is where you want the puck. That being said, just put it where you want it. It does not make that much difference.
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