Garmin GPSMAP 4008 Part 2

- Fishfinder Multi-Function Display

The Garmin GPSMAP 4008 is much more than a GPS: it can be a multi-function display centre for GPS, radar, fishfinder, AIS, video, weather reports and engine instruments - all you need are the relevant sender units and a few cables. I have already covered the GPS, video and AIS functions. The next thing to add is a fishfinder.

The Black Box

You need the box of tricks that converts the transducer signals into something meaningful to the display, and this is a little computer that can be hidden out of the way. I needed the digital version to match up with the GPSMap4008, which is simply mounted on a bulkhead and supplied with power (fused and switched of course)

The Transducer

You buy the transducer separately so there is a wide choice, and the better the transducer the better the fishfinder performance. Many fishfinders are supplied with very basic transducers and the difference between good and bad is significant. You can buy transom-mounted transducers with speed and temperature senders, but I have one of these on my Eagle unit and it is prone to weed growth and getting banged. You can drill a hole and mount a transducer through the hull, but I didn't fancy that so I went for an in-hull mount. Many transducers are in fact made by Airmar, regardless of badge, but for the few pounds extra it is worth buying the badged version (Garmin in this case) to ensure the right connectors are supplied. Mine has a neat angled housing to accommodate a deep vee hull and still point downwards. It is very easily mounted by gluing the mount to the inside of the hull, aligning the marks so it is perfectly horizontal, filling with antifreeze or mineral oil and plugging the transducer on top. The cable is then run to the black box and plugged in.

Connecting Up

Garmin has two methods of cabling and the easiest is the Garmin Marine Network, which is simply a cross-over network cable to connect the black box to the display. There are several ports so the display can act as a hub, or you can buy a hub separately if you have lots of units to connect. A two metre cable is supplied, but if this is not long enough there is a cheaper alternative than the expensive long Garmin cable: buy a standard network cable from e-Buyer for less than £2 and change one of the plugs to make it a cross-over cable. Instructions and a spare connector are supplied in the box.

Plug-and-Play

Once connected, the display unit recognises that a fishfinder is present and provides new menu options to allow full control of the fishfinder, various split-screen options, and even just displaying digital depth when the chart is displayed. The bottom image shows my preferred display for navigating busy areas. The dotted line shows my track (going back home in this case) with the AIS alarm switched to one mile. The Isle of Wight ferry is crossing slowly in front of me and a huge container ship is heading up the Solent on my starboard side. As you can see I have slowed to 6 knots and there is 79.9 feet of water under me as I round Gilkicker Point. The green vessels diplayed outside the warning circle are in fact anchored.

Manufacturers information is on the Garmin web site.

Expect to pay around £380 for the digital fishfinder and transducer

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