If mounting on the pedestal guard, one thing that most general retailers will not tell you is to check the manufacturer's warning (before you buy) for safe compass distance. Over half of the current plotters, maybe way over half, use a powerful perm. magnet to hold their little chip door closed. You want the model that uses a friction catch.
Look in their install manuals - available on line in pdf format - for this distance. It will range from 17 to 30 inches. We were allowed to borrow several new plotters from our local marine electronics shop and try them in the planed mounting position on the binnacle guard. Two of them noticeably swung the compass card 5 to 15 degrees. The model we chose did not.
Our local compass adjustor told me that some models, despite the warnings, will allow reliable use of the compass, but many will not. He is pragmatic and just sez to trial fit the location, watching carefully, and if it works, it works.
The underlying problem is that all of these companies, including the ones that buy full page ads in "sailing" magazines, engineer their products for the 98% of boating customers with smaller power boats. Those folks can locate instruments anywhere on a dash board, or.... just do not care about ever navigating with a compass.
The additional irony is that when surveying very similar products from a vendor group of companies like Simrad, Lowrance, and B&G, their plotters have no uniformity at all in use of these magnets. Same for Raymarine and Garmin.
It perhaps goes without saying... that like your flashlight, pliers, and portable vhf you park in the cup holder on that same binnacle, you will have to remove all those interfering devices, along with your suddenly-useless plotter,
if you lose power and fall back on compass and paper chart to navigate your boat.
Anyhow, just recall the advice from the Aged Knight to Indiana Jones when contemplating all of those cups:
"You must choose, but choose wisely, for as the real grail brings eternal life, the false grail brings death".
Interesting, the stuff you learn from movies!
:0
Loren
