The never-ending project to fill my hole in the ocean while bailing it out

Preparing for Sailing Season '07
Replacing the Depth Gauge Project

Description

A few years ago I installed a Humminbird Piranha Max 15 with a puck transducer in the bow.  It worked fine -- until last season's lightning strike.  During last year's Cape Cod cruise, it started going buggy:  sometimes showing 800 feet of water where I knew there was 100; 3 feet when I knew I was in 40.  A depth sounder, aka "fishfinder," is useful to me not only to know the depth so I don't run aground, but in navigation -- knowing the depth of the water and how it correlates with the charted depth.  I don't need to know if there are fish below, or what the ocean's bottom looks like, even what the water temperature is, but it did that too.  My unit had become extremely unpredictable -- therefore useless, even dangerous.  (May 5, 2007)

It was a bit of a nuisance remounting and unmounting the Max 15 each time I used my boat:  The connections at its back-end were difficult to connect due to the shortness of the wiring plugs and tightness of space behind it.  But it was too easily removable by "unauthorized" boarders, especially with my boat unattended out on its mooring for most of the time; too tempting.  So I'd remove it when done sailing, remount it when I got back out to the boat.  Unfortunately, it also took over the only place to lean back in the cockpit against the bulkhead -- the compass sticks out on the starboard side (see photo above).

Since installing the rope clutches, eventually I'll be able to remove the cam cleats on the bulkhead.  So I chose a Hummingbird HDR 610 depth gauge, which will mount flush with the bulkhead.  Yesterday's project was to remove the old "fishfinder" mounting bracket, its puck transducer, and the wiring and cable -- then replace it with the new depth gauge and puck transducer, rewire it.

The power and transducer cables run up alongside the cribboard finish trim, then over and out into the cockpit.  I'd drilled a ½" hole through the bulkhead when I installed the fishfinder, then had filled it with 3M 4200.  Getting that old bedding compound out so the connector plugs would pass back through was more time-consuming than I'd anticipated (there is zero tolerance}, but with perseverance it was accomplished.  I removed the old transducer and its cable then ran the new cable aft.  (see details below)  Done with that, I epoxied the new transducer in place in the bow and left a block of granite on it overnight to secure it to the inside of the hull as the special slow-drying epoxy that came with the gauge cured.

With the cabling and plugs removed, first I wet-sanded the gelcoat beneath the old fishfinder mounting bracket as best I could using 1000 then 1200 grit:  It'll never be a perfect match, as it was protected by the mount, but the result was a big improvement.  Then I filled the screw holes with West System epoxy resin mixed with a little colloidal silica and a touch of white tint.

Finally, I used the 2⅛" hole saw I'd borrowed from the boatyard and cut a hole for the new depth gauge.  I tested the fit, which was fine if a little loose.  With the hole cut, I mixed another batch of epoxy resin and "painted" the plywood core sandwiched between the exterior and interior fiberglass.  The epoxy filling the screw holes still needs to be sanded smooth with the bulkhead, but as the day was ending and I had questions about the new unit's connections and power supply (and an on/off control), I taped up the hole for the night and called it a day.  (Note how less noticeable the gelcoat discoloration/oxidation is when your eye is drawn away.  This works the same when removing old boat names from a transom!)

This morning began "unseasonably cold" (in the low 40s) so I didn't get back out on the boat until after noon.  The tape had to be removed, the epoxy sanded, before I could move on.  (May 6, 2007)

Once the tape was removed, I sanded the epoxy patches over the old screw holes with 320 grit, then wet-sanded the area again with 1000, then 1200.  It was as good as it was going to get.

From there, I put a thin bead of 3M 4200 around the hole and pushed the new Humminbird HDR 610 into its new home.

It's looking good so far.

On the backside, in the cabin, I finger-tightened the wing-nut:  I'll tighten it up more tomorrow, after the bedding compound has had a chance to cure.

The confusion over whether there is an on/off button on the unit stalled me yesterday.  (Apparently this model doesn't have one, according to folks in the discussion group and from my weekend research.)  In the end, I added a toggle switch (bottom left in the photo).  It took drilling a ½" hole for the toggle switch.  Now I can wire  up the depth gauge and its fuse, plug in the transducer cable, attach the alarm buzzer, and be done.

Detail:  I removed the old puck transducer beneath the aft v-berth compartment, against the cabin bulkhead, then replaced it with the new one.  I used a beveled putty knife to scrape off the old epoxy down to the fiberglass hull, then acetone to clean the spot again.  Once it was clean and dry, I used the package of slow-drying epoxy that came in the Humminbird package and buried the transducer into it, twisting slowly back and forth as I worked it in.

After moving the cable out of the way, I placed a granite block on top of the transducer overnight, until the puck was securely embedded.  The next day I plastic-tied it to other cables running aft alongside it to keep things neat.