Chart plotter Installation

For all my years sailing I’ve used a hand-held GPS – when I had a GPS. For a very long time, I just used the tried and true method of paper charts, compass (fixed and hand bearing), dividers/parallel rule, and speed estimate or mechanical speedo.

I’ve had two different hand-held GPSs  (well, three actually . . . I sat on one in rough weather and broke it).  Of course, the hand-helds work fine. They give accurate position and speed over ground, and the ones I’ve had included a graphic screen with rudimentary charts on board – you can see your position on a map. The map, however, is small and it’s difficult to read. Additionally, manipulating the curser can be slow and cumbersome.

I was given an older Raymarine GPS 435. This obviously is not a state-of-the-art instrument, but it is quite an improvement from the tiny screen I’ve been looking at for so long. In fact, the manual I downloaded is dated 2004, so it’s quite a few years mature.

So the first thing to do was to find out if it actually worked. I took it to the boat and attached the power leads (red and black) to pos. and neg. terminals, respectively. No joy. I was disappointed, but then decided there was nothing to lose by reversing the leads – black to pos, red to neg. And it powered up! Now, I just have to ask. . . who does this, and why? Why would you make red the ground lead? The only answer I can imagine is that it’s a product of the UK, and they just do things differently there. Regardless, the unit powers up. Now I need an antenna. On a trip to Florida last fall I stopped at Sailors’ Exchange in St. Augustine (salvage boat parts store ) and found a Raymarine passive antenna for $25. Perfect. A couple weeks ago I began the installation.

First decision: Where to install? Do I want a bulkhead mount? That means it stays out in the weather all the time. Then I remembered – when I first bought Cay of Sea she sported an ancient Loran unit that didn’t work. I removed it, but saved the bracket upon which it was mounted. The bracket was mounted in turn on a piece of teak stock that was attached to the bulkhead with a pintle and gudgeon – a swing mount. I dug through my old boat parts and found it! After a quick sanding and application of varnish, it was ready to go.

That was easy. . .  The hard part was wiring, but only because I had to chase the wiring from the fuse panel, and the antenna coax from the stern rail. Fun time in the cockpit locker. Emptied most of the locker contents and replaced it with myself, then wriggled back to the stern. Fortunately the coax was within easy reach, and all I had to do was support it with zip ties to existing screws. The unit is installed on the opposite side of the boat with respect to the cable runs (of course!), so a partial dismembering of the interior joinery was required to fish the cables underneath the bridge deck area over to the starboard side. After cutting a small relief in the top of one trim panel, I was able to pass both cables through with minimal destruction.

Making the electrical connections was a bit more challenging, but only because my test light was faulty (c’mon, I repaired it with duct tape two years ago!). Not being able to get a consistent signal with the test light, I broke out the multimeter and found the hot side of the circuit breaker. After crimping a few wire fittings and attaching them to the right contacts, and I had power. But before buttoning everything up, I powered up the GPS just to make sure.

From a scrap piece of teak, I fashioned a mounting disk for the antenna. I attached the disk to a dowel which I inserted into a piece of pvc pipe zip-tied to the stern rail. The cable passed through portside passive engine room vent.

The final installation looks like this:

Now, when life approaches normal again and Maryland DNR lets us begin boating (post-covid-19), we can enjoy sailing and using the “new” instrument.

4 comments
  1. Eolian said:

    We love our chart plotter! And with it hooked up to our autopilot, it nicely corrects for our prodigious currents, keeping us on our desired course!

    • Cool! Mine could do that, but the tiller pilot doesn’t take nmea input. No worries – too much convenience would be bad for me!

  2. Elizabeth said:

    Wow, Dad! you have been so busy!! You’ll have to have some kind of grand tour to enjoy it all once you’re allowed out again.

  3. Hoping to take a lovely longish cruise when the virus ban lifts!

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