Monday, February 11, 2008


GPS/VHF Wiring, 2/9/2008

I installed new electronics last spring, but to date had not yet completed the wiring for the GPS. That means our DSC capability for the radio wasn't complete. We could make an automated digital distress call, but it would not include our coordinates. That would certainly complicate a search and rescue should we ever be unfortunate enough to need it.

On Saturday, I finally finished off the wiring. The instructions for the Standard Horizon radio indicate three connections: data in(+), data in(-), and data out. The GPS instructions only indicated data in and data out (no polarity on the data out). Standard Horizon tech support was very helpful, and advised me to make connections as follows:

VHF blue (in+) to GPS blue (out)
VHF gray (out) to GPS yellow (in)
VHF green (in-) to ground

I ran a power/data cable for the GPS to both helms, and joined them at the lower helm. From there, I ran the red and black wires to the switch and ground bus, and the signal cables to a new 4-post block. I then ran a length of signal wire up to the radio, and attached it to a quick connect so that I can easily disconnect the radio when I want to remove it from the boat. The worst part of this project was handling the very fine signal wires, which are difficult to strip and separate without cutting them.

Looking forward to trying out a ship-to-ship DSC call this summer!

Sunday, February 10, 2008


Galvanic Isolator, 2/9/2008

As I mentioned earlier, one of my planned projects was installing a galvanic isolator. This was recommended, but not required, by both our surveyor and BoatU.S.

Although Mariner II wasn't showing any serious problems with corrosion, zinc loss during the summer is difficult to address, as it involves diving under the boat (which I did once this past year). Diving under to replace a zinc isn't that bad as long as the sea nettles aren't there keeping me company, but usually they are. A galvanic isolator should, minimally, slow our zinc loss enough so that it can be replaced once per year, during winter haulout.

I considered several brands, including Guest, Yandina, and ProMariner. Ultimately, I installed the ProSafe 30, without a monitoring system. ABYC recommends that galvanic isolators be self-tested and monitored to ensure that the AC ground wire is uninterrupted. The isolator alone does not meet this recommendation, but thousands have been installed this way without problems long before ABYC made their recommendation. Since the monitoring system costs more than the isolator itself and complicates installation considerably, I opted to skip it for now. The ProSafe 30 does allow me to add the monitor later, but for now I will just plan to test it routinely (spring and fall) with a diode tester. The test is easy: with shorepower disconnected, attach one lead of a multimeter (in "diode test" setting) to each side of the isolator and get a reading. Switch, and test again. Both readings should be the same (within 10%), and both between approximately .7 and 1.5 volts.

On our boat, the isolator fit nicely in the starboard storage area below the helm. I was able to simply cut the ground wire, attach insulated ring terminals, and connect them.


I spent most of yesterday doing some work on the boat, so I'll have some updates shortly. In the meantime, a long-overdue update on the Jabsco oil-change pump issue: I received a replacement unit, free of charge, in 2-3 weeks as promised by Jabsco. Outstanding customer service -- no hassle, no question, they stood behind their product.

More on boat maintenance to come soon...