This page was last updated on 16 May 2004.

Knotmeter/Depthsounder | GPS | VHF | Radar | Laptop Computer and GPS Interface | Wind Instruments


We are installing a Horizon 150 series multi-display for the knotmeter/depthsounder.  This combines both functions in a single unit.  Installing the display could hardly be easier:  determine the location, drill a single hole with a holesaw (I think it was about 1-1/8") and install the unit, using a supplied foam rubber gasket as a seal.  There's a plastic nut that just screws onto the protruding part of the back of the instrument.  Done.

Installing the two through hulls took several hours, all told, including the thought that went into their eventual location.  I went back and forth on the locations, trying to come up with the best compromise of convenient interior location vs.. efficient exterior location.  There were things in the way that prevented locating the fittings where it might have been ideal.  In the end, I decided to mount the knotmeter just below the turn of the bilge in the keel, so that the impeller is effectively vertical.  I decided to mount the depthsounder transducer on the starboard side near the vanity sink drain, just aft of the main structural bulkhead (the one beneath the mast step).  This location seemed to offer the best compromise of accessibility from the inside while retaining a spot outside that would be least affected by the keel shadow.

I drilled pilot holes from the inside out in both locations, then went outside and drilled the holes out with a 2" hole saw.  I drilled the depthsounder hole more or less vertically, which made for an oblong core sample.  Then, I sanded the bottom paint off the areas surrounding the two holes, so that the sealant would have the best adhesion, and cleaned them with acetone.

The depthsounder needs to be mounted vertically for best performance, so I had to make a wooden fairing block for the outside of the hull.  Of course, the inside needs one too to give the nut something to bear against.  Making the block involved estimating the deadrise of the hull with a bevel gauge, transferring the angle to a piece of thick mahogany stock, and making the angled cut on a table saw.  Then, I drilled 2" holes through both pieces (for the through hull) and test fit everything a few times, fine tuning as necessary.

depthgoop.jpg (28248 bytes)Next, I heavily gooped up the fittings with 5200 and pressed them into place.  I wasn't shy with the sealant, as I wanted a good seal.  It always pays to use way more than necessary, and clean up the excess later.  I gooped the fairing block too, as well as the threads on each fitting.  Because of the adhesive qualities of the 5200 and the tight holes, I was able to do this alone without worrying about the fittings falling out.  I went inside the boat kmgoop.jpg (28896 bytes)to install the stop nuts on each fitting.  The plastic knotmeter fitting comes with a rubber interior gasket that helps accommodate the slight irregularities of the hull; all I had to do was tighten it down hand tight, making sure that the notch in the fitting was aligned fore and aft.  The depthsounder is bronze, and required an interior fairing block because of the angle.  

I spread a little 5200 on the hull beneath this block as well, pressed it into depthoutside.jpg (30848 bytes)kmoutside.jpg (22184 bytes)place, and threaded on the stop nut.  There's just enough threads exposed to allow about 1-2 full threads to pass beyond the nut when it was fully tightened--barely  made it!  I tightened it hand-tight and went outside again to check the positioning of the fairing block.  Then, I used channel locks to tighten it down as much as I could before the fitting began to rotate.  I went back outside and cleaned up the excess that had squeezed out.

depthinside.jpg (29788 bytes)kminside.jpg (40624 bytes)Interior of depthsounder and knotmeter fittings


We have a Garmin GPSMAP 175, a great unit with built-in plotter.  It takes G-map cartridges.  This is a handheld unit, so we purchased the appropriate brackets, external antenna, and power supply cable for semi-permanent installation.  We also purchased a swing-out mount that will mount inside the companionway, allowing the unit to be read from the cockpit.

gpsantenna.jpg (37760 bytes) installed the antenna on the stern pulpit.  It screws into a standard antenna bracket, which clamps onto the pulpit.  I ran the wire down the outside of one of the supports to deck level, then through a cable clam into the lazarette.   The cable clam actually looks like it will work; you drill a hole through the deck and install the bottom piece, then drill a hole the size of the cable through a rubber wedge.  After slitting through the wedge to gpsclam.jpg (56276 bytes)one side, you can slide the cable in.  The whole thing is then wedged into place with the top piece, squeezing the cable tightly in the rubber.  I ran the cable up to the cabin through the port cockpit locker, securing it along the way as needed.

gpsin-1.JPG (173332 bytes)To mount the unit, I purchased a Garmin bracket for my particular unit, as well as a swing out bracket that I mounted on the inside of the companionway.  I also purchased the Garmin power/data cable assembly.  I installed the brackets as required, and ran the power cable and antenna cable up to the units, keeping the cable run as neat as possible, since it will be exposed.  The bracket allows the GPS to be swung out for cockpit gpsout-1.JPG (161628 bytes) viewing, or left in the cabin for use there.  It's a pretty slick system; it makes the GPS very readable and usable from the cockpit, which is really where you want it.  The dodger protects the GPS from spray and rain when in the out position.

woodgpsbracket.JPG (148854 bytes)I had to slightly modify the GPS bracket and installation to accommodate my new radar.  This entailed moving the bracket to the bottom of the companionway and adding a mahogany platform to extend the bracket's reach an extra 3" or so to clear the radar display.  See more about this here.

gps48.JPG (152411 bytes)Update!  For a backup, I purchased a nearly new Garmin GPS 48 handheld.  These are great little units, and I found one for a great price thanks to Ebay.  I wanted a backup in case something happened to our main unit, and also a small one for travel, to take in the dinghy, and, God forbid, to keep in an abandon ship bag.  It's  tiny--about 6" x 2"--and runs on AA batteries.


The VHF is a West Marine Aurora.  It's pretty basic, but we don't need it for much more than calling the launch at the end of the day.  We also have a couple handheld radios.  During wiring operations, I ran the power supply from the panel to the VHF location--on the port side above the icebox.  I also ran a length of coax up to the mast area, leaving extra for the final run through a waterproof fitting in the deck.  I will run another length through the mast to a new antenna.

I installed the VHF next to the electrical panel, above the icebox.  With the mast stepped, I made up the antenna cable connections using Shakespeare center pin PL-259 connectors, which seem to work well.  The power cables for the VHF run behind the trim panel to the electrical panel next door.

Update!  In addition to the fixed mount VHF, we have three handhelds.  I have an older ICOM IC-M5 (on the right in the photo below) that is a great, rugged radio, but the battery doesn't contact properly and it doesn't always work.  Usually, fiddling with it and removing and reinstalling the battery gets it to turn on, but it's unreliable for general use.  It makes a good backup, though, or one to bring up to the vee berth at night so I can listen to the weather reports.

To supplement the old ICOM, I bought a Horizon HX150S (on the left in the photo to the left) a couple years ago.  It worked fine until this year, when for some reason it seemed to stop working properly.  I couldn't get weather on it, and it didn't seem to transmit (or maybe it just doesn't receive.  Perhaps it's a battery issue--I may get a new battery pack for it.  Supposedly, the radio can operate on standard AA batteries, but they don't just slip in in place of the standard battery pack--I've never really tried.  Anyway, I was disgusted with this radio this past season, and decided to look for a good replacement.  Naturally, as I tend to do now--a recent infatuation--I turned to Ebay.

I found a nice new ICOM IC-M1 (in the middle), and won it for less than half of its list price.  It's very nice--just got it.  I really like it, although I haven't really used it or anything.  But it's a nice size, and is high quality as well.

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Glissando, Pearson  Triton #381

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