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How to Install a Chartplotter

For this how to install a chartplotter article I will be removing a older Northstar 6000i and replacing it with a new Garmin 740s chartplotter fishfinder combo unit. An Icom VHF radio will be retained. All the gear is to be flush mounted on a panel in the boat’s center console.

Because this installation will have the 740s display flush mounted in a console under a T-Top I decided it would be best to also install an external GPS sensor. To begin this marine electronics installation I carefully removed the old display, VHF radio, and the panel in which the gear was mounted.

garmin 740s and icom marine vhf radio flush mounted on grady white center console

Here is the completed job with the Garmin 740s and the Icom radio installed in the Grady White center console.

Care was taken to not damage the VHF radio as it would be reinstalled. I also wanted to save the panel in which the gear was mounted so I could use it as a template to cut out a new panel or reuse it if possible.

Install External GPS Sensor

The first part to arrive for our install a chartplotter operation was the new Garmin GA30 external GPS sensor, so I’d begin here. There was an external GPS sensor already installed on an aluminum stanchion on the T-Top for the Northstar unit.

My first job was to unscrew the GPS sensor from the stanchion while saving the connected cable so I could use it to pull the new cable.

From inside the console I used electrical tape to connect the old cable to the new one.

Then I pulled the new cable up from the center console through an aluminum tube supporting the T-Top into view on top of the T-Top. From here I screwed GPS sensor base onto the stanchion, attached the sensor cable, and finally snapped the sensor in place.

Pulling Cables and Wires on a Boat

Pulling wires and cables on a boat are never easy and a GPS antenna cable with the terminal ends already attached can be really troublesome. However, this time because of the short cable run and the large inside diameter of the aluminum pipes the job was easy and straightforward with no surprises.

In some circumstances the terminal end must be removed from the cable to facilitate routing. Don’t ever cut a GPS antenna cable without first consulting the manufacturer. Some cables can be cut and some cannot.

The Garmin 740s also has sounder capability and did require installation of a new transom-mount transducer. I cover this part of the marine electronics installation in a dedicated article titled How to Install a Transducer.

Install a Chartplotter—Mounting the Display

Flush mounting the 740s was fairly easy. The unit is supplied with a stick-on template to making drilling mounting holes and making the cutout a simple affair. In this case, I was able to reuse the old panel by slightly enlarging the opening left by removal of the Northstar 6000i display and drilling new mounting holes.

The Garmin 740s was through-bolted in place on the panel with stainless steel fasteners. Accompanying bevels cover the bolt heads and make the installation look very clean.

Wiring Up for Interface with the Marine VHF Radio

This installation required making a connection from one NMEA0183 port on the 740s to the Icom marine VHF radio. This would allow the radio to receive position data from the GPS for full DSC functionality. I followed the wiring diagram in the Garmin 740s installation manual to make the needed connections.

The circuit is completed by connecting two very small wires. One easy way to make these types of connections is to twist the wires to be connected together with your fingers, then make a quick solder joint, and finally add a short section of heat shrink tubing to seal it all up. I use pliers to squeeze the open end of the tubing while it is hot to seal the end. Make sure when you are all done the wires are secured in place with tie-wraps or cable clamps.

garmin 740s and icom marine vhf radio in panel

Both the Garmin 740s display and the Icom marine VHF radio were installed in the panel before it was put into its final position in the console’s built-in electronics box. To beef-up the panel around the large display cutout strips of heavy plastic were added above and below the display and fastened in place with the four display unit mounting bolts.

Install a Chartplotter—Connecting Power

Power to the Garmin 740s was supplied by a bus bar located inside the center console. An inline fuse holder was attached to the positive wire coming from the power/data cable harness using a heat shrink butt connector.

Ring connectors with heat shrink tubing finished off the wire ends. Once the wires were attached to the proper place on the bus bar, black to negative and red to positive, they were run up into the electronics box from below. With all the electronics out of the box and the front panel removed the wire harness was secured in place. Enough slack was left in the harness to allow easy removal or installation of the front panel. Make sure the fuse placed into the inline fuse holder is the correct size.

Final Mounting of Marine Electronics

One of the last things to do is actually install the panel containing the electronics. With only one display and one radio in the panel it was easy enough for me to hold the panel myself and then attach the GPS sensor cable and power/data cable to the 740s as well as attach the radio wires. Next I slipped the panel in place and secured it into position with six stainless steel screws.

Finishing Touches

With the install a chartplotter operation complete, I powered up the 740s and radio and quickly worked through basic setup menu selections. Once the 740s had acquired a position lock I checked to make the VHF radio was also receiving position data. Lastly I downloaded the latest software from the Garmin website and using a blank SD card installed it.