Mark Fritzer reports in from Palmyra, and brings us up to date on wonderful snorkeling and further experimentation with the high powered DC charging system. With comments on navigating with active SONAR in the tropics:

We spent most of the day yesterday working on various maintenance items around the boat. Obviously, the list of maintenance for the completion of the cruising season once the boat arrives in Hawaii is extensive, but there is always a list of minor things that need to be done on a boat, so we tried to knock some of them out. As I mentioned before, the oil in the main was changed and while at it, we checked the zincs, air and bypass return filters, transmission fluid, belts, etc. and added a few items to the “it sure would be nice if they could do this on future boats” list. A couple of those items, such as captive studs on the floor bolts of the engine guard instead of bolts with washers, and modifying of the Murphy coolant gauge mount to make zinc access easier, have made it to the top of my list to discuss with everyone once I return. We also removed the rectifiers assemblies and flipped the fans over. After some testing at Circa, they found pushing air over the rectifiers cooled them better than drawing it through. I brought an alternator temperature sensor with me from Seattle, and we installed that on one of the rectifier assemblies to see if it helps to control the alternator temperature, by throttling back the charge output as the heat rises. We will test the results when we leave Palmyra. In the afternoon, captain Steve and I went out to a couple of the local snorkeling sites for a quick look around. Hands down, this is the most amazing snorkeling I have ever done. The reef and its inhabitants are simply astounding. I have never seen coral as colorful or dense, and the array of different sights is hard to describe. Hopefully, I will be able to post some photos upon my return to show what words would be hard pressed to describe.

We left Palmyra this morning at 0730. We are all sad to leave this incredibly well-maintained island paradise. The feeling is bittersweet, as we are all ready to be on the sea again and headed towards our destination, but have been touched by the significance of what we have seen here on the island. If you ever get the chance and have the time to jump through the very necessary hoops, I highly recommend making this stop your number one priority. Having a certification saying you have been inspected and cleared of carrying rats aboard, and a fresh hull cleaning are some of the easy, but mandatory steps required for entry. I would go so far as to bypass some of the other islands along this route to spend more time here. The scientists, Nature Conservancy, Fish and Wildlife and benefactors are all doing an incredible job of maintaining what may well be one of the last functioning reef ecosystems left in the world.

Seeing the sides channel here that was blasted out of the reef by the Navy on the Furuno sonar makes me realize just how invaluable this piece of equipment can be to the voyaging cruiser. The ability to not only scan ahead, but the width, range and scope of the scan could be a game changer for those venturing off the beaten path. The course we are currently on is a good example. There are small buoys visible in the daylight that mark the channel, but that’s it. If you had to venture through here when visibility is poor or non-existent, it would be extremely hard and stressful to do so. Fortunately, the electronic charts match reality, but that is often not the case. Captain Steve was telling me that in the Marquesas and parts of Fiji, the electronic charts can sometimes be off by a half mile. Considering the faith that can be put in some of our modern day electronics, that could be catastrophic. A side note and reminder to that is that carrying current paper charts, and knowing how to plot a course on them, is still the best way to accurately know where you are. However, having forward-looking sonar with the capability to turn, rotate, and scale is a darn good tool to have at one’s fingertips.

When we fired up the main this morning our batteries were down to the 45% SOC level and reading 24.84 VDC. The ambient engine room temp was 91°F. Within a couple of minutes of firing up the main, both alternators had ramped up to 153 and 151 amps. They ran this way for about 10 minutes as the temperature slowly climbed. When the temperature at the rectifier that had the alternator temp sense lead climbed to 248°F, the regulator suddenly cut the alternator outputs back to 103 and 101 amps. The temperature started dropping and when it got back down to around 198°F, the regulator let the amperage climb back up again to the 150 amp range. Once there, the temperature immediately started to climb again back up to around 245°F. At that point, the regulator once again throttled the output back to the 100 amp range. It’s been cycling like that for several hours now, and as I have been monitoring the temperature of the regulators, seems to be keeping them within an acceptable temperature range. On one of my trips to the engine room, I put an amp clamp directly onto the AC then DC outputs and disconnected the temperature sense leads from the regulator. The amperage immediately shot up to full output and the temperature started to climb. I let it go until the regulators hit 300°F and then reattached the temp sense leads. Immediately, the amperage dropped back to 100 and 103 amps DC output and the temperature started to drop accordingly. An interesting side note is 3 wires connect the AC output from the alternator to the rectifier, one for each phase. Each of those wires carries roughly 1/3 the DC output current and 2/3 of the nominal DC voltage in AC. Knowing these numbers can help in determining if there is a winding issue starting to develop within the alternators themselves.

Well, back to life at sea and it’s time for my watch.