Garmin GPSmap 4xx — How useful is a mini (4-inch) chartplotter?

On a small sailing yacht, power consumption is a real issue, particularly on passages. A wind generator is typically useless on a downwind course and often the sails shade the solar panels and there might be days with a thick cloud cover. Some electrical devices can be assumed to be running 24 hours a day: the fridge, some instruments (e.g. log, wind, …), a VHF radio, and in our case also an AIS transceiver blackbox. (Cruisers who rely on an electric autopilot usually don’t worry that much about power consumption since they need to run a Diesel or gasoline generator regularly anyway.)

What about a chart plotter? First of all, why would we need a chartplotter 24 hours a day at all? In our case the answer is (a) to have an AIS viewer which issues AIS alarms, (b) to view speed and course over ground and (c) to view the great-circle route and the deviation from it. Of course there are small, dedicated devices on the market such as stand-alone AIS viewer or ordinary GPS devices which could do the required jobs, but we don’t have them.
Running a chartplotter with a nice and large display (e.g. 8 inch or even larger) all day long, most likely consumes too many amp-hours. E.g. our Simrad NSE8 (8-inch display) draws around 2 amps. Its larger sibling, the NSE12 (12-inch display) requires even 3 amps, i.e., it would eat almost 72Ah per day.

In addition to our NSE8 at the nav station inside we also have a mini chartplotter at the helm in the cockpit. It’s a Garmin GPSmap 421 with a 4-inch display. The nice thing is: it draws even less than 1 amp and we can run it continuously when underway.

We installed it on its swivel bracket such that we can view it from behind the wheel (typical chartplotter-aided navigation), when sitting in the cockpit in front of the wheel (our classical watch position on passages) and even when looking up the companion way from the saloon. I don’t think that a larger plotter could be mounted so versatilely. It is tiny, and indeed, we have seen dinghies with larger plotters (or fish finders), but for our overall setup the 4-inch Garmin–nickname Armin–is the ideal cockpit instrument.

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