In November 2012 we bought a Garmin AIS 600, Automatic Identification System Transceiver. We chose this product for several reasons. We have a Garmin 4208 chartplotter and this is compatible. We wanted both send and receive capability and the ability to connect to our existing VHF radio antenna without a splitter. This product has all of that.

We installed it ourselves. We received some defective units at first and went through three before we got it working. Garmin’s technical support team was great. We were very happy with it once we got it up and running.

AIS works by sending and receiving digital information using the VHF radio band. Typically the AIS receiver and transmitter use the same antenna as your VHF radio. Some products need a splitter to share the antenna. The information transmitted includes latitude, longitude, MMSI number, vessel name, speed and course. The unit has a GPS to provide some of this information. The rest is programmed into the device.

The AIS 600 sends the information about your vessel over the VHF airwaves for other vessels to receive and sends information about other vessels to your chartplotter over NMEA 0183 or NMEA 2000. You can also see vessel information on PC-based applications via a USB cable.

We connected our AIS 600 to our chartplotter via NMEA 0183. We can also display other vessel information on our Windows PC or tablet running  OpenCPN or the Garmin setup program for Windows.

OpenCPN with AIS
OpenCPN with AIS

We were very happy with our Garmin AIS 600 until it didn’t work. Actually, it only stopped showing vessel information on the chartplotter. It still transmitted our vessel information and we could still display vessel information on our Windows tablet.


Whenever something stops working, and I’m not sure why, my first step is to procrastinate. Sometimes it will start working again, or at least I find out why it stopped. Once I determined that it wasn’t going to fix itself, I checked the connections between the AIS 600 and chartplotter. I re-soldered the NMEA 0183 connections and checked them with an ohmmeter. Everything checked-out good.

Garmin AIS Setup Utility
Garmin AIS Setup Utility

I Googled “garmin ais 600 problems” to see if I could find any suggestions. I found a Garmin support page. This was geared to first-time setup problems. I did it anyway. I updated our Garmin 4208 chartplotter to the latest firmware and checked the NMEA 0183 settings. The NMEA 0183 port used for AIS must be set to high-speed (38,400 baud vs. 4800 baud). It still didn’t work.

I emailed Garmin support. They replied, but I had already tried everything they suggested. I reread the installation manuals for the chartplotter and AIS. I rewired it to use other NMEA ports on the chartplotter, but it didn’t help.

I suspected that the NMEA 0183 stopped working, but I didn’t know if it was the AIS or chartplotter. I wired the output of the AIS NMEA 0183 to a serial to USB adapter. The adapter that I had did not work with the current version of Windows. I bought a new one on for $8.99.

Windows used to include HyperTerminal, a terminal emulator. Windows 10 doesn’t include that accessory anymore, but I had another program, PuTTY, that could be used in its place. I hooked it all up. I could not see anything on the AIS NMEA 0183 output, but I could see valid NMEA sentences on the AIS USB output. I was almost certain the problem was the NMEA 0183 output o the AIS 600.

PuTTY connected to AIS
PuTTY connected to AIS

A Garmin technical support rep called me to find out how it was going. He said it would cost $450 to repair the AIS 600. We discussed using NMEA 2000, which is supported by both the AIS 600 and 4208 chartplotter. That required a NMEA 2000 Starter Kit. The starter kit cost $87.95 on This looked like my best alternative.


The AIS 600 came with some NMEA 2000 parts. The NMEA 2000 Starter Kit had everything else I needed to connect the AIS to the Chartplotter.

NMEA 2000 networks are powered by a 12 volt source. We wired ours to the same circuit as the Chartplotter and AIS. Our network consists of a backbone with three T-connectors and a backbone extension cable. The middle T-connector is the power cable, the others connect to the AIS and Chartplotter with drop cables. Each end of the backbone is terminated.

NMEA 2000 Sample Network
NMEA 2000 Sample Network

The above diagram is from Technical Reference for Garmin NMEA 2000 Products.

We connected the network to temporary a power source and verified that it was working in about 10 minutes. The permanent network wiring was pretty easy as well. We set it up so that we can easily attach other devices, such as a wind instrument. One more to do item to check off the list.

Weather, Part 8

It’s been a while since I did a weather post. I thought I had covered everything, but when I wrote Dry Tortugas – Day 6, I wanted to reference a post about GRIB files and realized that I never wrote that post. So here it is.

Cruisers have used GRIB files for a while. GRIB stands for Gridded Binary file, which describes the format, not the content. But most cruisers accept it as weather data, in particular, raw data from the Global Forecast System (GFS) model.

GRIB files are raw data from a computer model and have their advantages and disadvantages. Unlike Radio FAX weather maps they are not interpreted by a human, but a GRIB file has data for multiple locations over periods of time. GRIB files are more complex than weather FAX files and need a program to interpret them.

There are many ways to work with GRIB files. We use AirMail for it all.

Getting GRIB Files

We get GRIB files by sending an email to SailDocs. A minimum request message specifies the model and area of forecast. There are other optional parameters such as grid spacing and Valid Times (VT). The AirMail program has a GRIB-Request window to help format a request.

AirMail Grib-Request Window
AirMail Grib-Request Window

There is a trade-off between the amount of data needed and the file size. We tried out different parameters before we started our cruise to Dry Tortugas. Here is what we ended up with.

Subscribe GFS:26N,21N,084W,072W|1,1|0,12..120|PRMSL,WIND TIME=00:00

The above message is a single line. It has the following meaning:

  • Subscribe asks to get a new file daily. Use Send for a one-time request.
  • GFS is the model.
  • 26N,21N,084W,072W are latitudes and longitudes of the area the file will cover. We get a big area because we like to see weather from Dry Tortugas to Bahamas.
  • 1,1 defines the grid spacing in degrees (Lat,Lon).
  • 0,12..120 define the Valid Times (VT). In this case it is requesting the current forecast, followed by the 12 hour forecast, and 12 hours thereafter until 120 hours. We like these times because they correlate to the NWS 5-day zone forecast.
  • PRMSL requests Mean Sea-Level Pressure.
  • WIND requests gradient surface Wind.
  • TIME=00:00 specifies the UTC time that the file is sent. This time works best for us when we are cruising because we get our emails in the evening when the SSB propagation is good.

More information about requesting GRIB files is available at

Viewing GRIB Files

There are many options or viewing GRIB files. We use the viewer that comes with AirMail.

AirMail GRIB Viewer
AirMail GRIB Viewer

This viewer shows wind barbs and isobars for the area covered. It shows wind speed/direction and pressure wherever you place the mouse cursor and wind speed/direction at your current location, as set in AirMail. Select a Valid Time (VT) or scroll through them using up or down arrows to see the forecast for that time period. We usually set our location and scroll through Valid Times to see wind for our location for the next five days.

GRIB files play an important role in cruising. Especially when combined with other available weather resources. A GRIB file might even be the most important weather resource when in remote areas, without cell phone or internet access.

Dry Tortugas – Day 9

We wake up at 5:20 to rain. We quickly shut the windows and hatches. The rain stops by the time we get everything closed. It’s almost time to get up anyway.

We don’t have far to go today, but we want to get back to the marina before the wind and seas get too high.

Our refrigerator was running when we went to bed, but it started blinking lights during the night so we turned it off. We start the generator and run it on 110 volts AC. It runs fine that way.

Our holding tank is doing good. We partially dumped it five days ago on the way to Dry Tortugas. We could go a few more days, but we will get a pump-out when we get back to the marina.

We pull the anchor at 6:50 and exit the harbor. We turn east and head to our marina and we are heading directly into the wind, with seas about 1 foot.

We get back to the marina at 10:15.

This was a good trip. We came back with a long list of “To Dos” but most of them are easy fixes. Lots of things worked perfectly We had a great time exploring Marquesas and Dry Tortugas. It was especially fun with George and Nancy.

Dry Tortugas – Day 8

The wind dies during the night and the boat fills up with no-see-ums. Fran gets up and closes the hatches and windows, but it is too late.

We get up at 5:30, make coffee, and add oil to the engine. We start the generator for the refrigerator. The food inside is still cold.

Originally we talked about anchoring in Newfound Harbor, but since we went further yesterday, we decide to anchor in Bahia Honda tonight. We’ve always wanted to anchor there and we might even dinghy in to the concession store and get ice cream.

Questeria Leaving Boca Grande
Questeria Leaving Boca Grande

We put out our trolling rods and catch a barracuda. We can’t get the hook out so we end up cutting the line and losing our lure. No more fishing today. George and Nancy decide to go out to the reef and fish for yellow tail. We want to get to the anchorage and let the boat cool off and check on the refrigerator.

We get to the Bahia Honda anchorage at 3:00pm. We are the only boat in the anchorage. When we go to drop the anchor, the windlass remote does not work. We have to use the control switches in the cockpit. It is easier with our EarTec headsets. We anchor in 9 feet of water. We have heard that there is a strong current here so we put out 7:1 scope. Adding 6, the height of our anchor shoot, to 9, the depth, and multiplying by 7 comes out to 105 feet.

This is the first time we have anchored here, but we are familiar with the Bahia Honda state park because we stayed here in our RV in January. See RV Adventures, Sault Ste. Marie to Marathon, Bahia Honda.

The refrigerator has run on the generator all day. We turn off the generator and the refrigerator runs on 12 volts.

This a noisy anchorage. There is road noise from the Bahia Honda Bridge and there is a lot of boat traffic from the state park and boats going between Hawk Channel and the bay-side. Worst of all is the people on the beach blasting their music.

Steel Lady comes in at 5:00 and anchors 100 yards west of us. Another sailboat comes in behind them. A woman in a thong is out on deck with a boat hook. First they try to moor to a crab pot buoy, then they go to the mooring ball that is for official use only. When they see that they can’t use a mooring ball they decide to anchor right on top of our anchor. We call them on the VHF radio and tell them they are over our anchor. He comes back and asks how much rode we have out. We tell them over 100 feet and they move. We thank them.

We watch the sunset and blow the conch shell. The park closes at sunset (except for the campgrounds) and the loud music from the beach stops. At 9:00 we run the A/C to cool the boat. The refrigerator is still running on 12 volts. The road noise and boat traffic subsides.

Dry Tortugas – Day 7

It starts to rain at 1:30am We wake up to rain pouring in our hatch. The bed is soaked by the time we get the wind scoop off and the hatch closed. The wind is howling – maybe 25 to 30 knots. We dry  ourselves, the bed and the floor. I go back to bed. Fran says “In a wet bed?” I reply “It’s only wet in the middle.”

A few minutes later Fran is calling me. Our shade is trying to blow off. She is holding a corner and wants a piece of rope so she can retie it, but sees the grommet is torn out. We decide we need to take it down. It is tied in some places and we have to cut the ropes with a knife, but we get it down and out of the wind.

While we are doing this boats around us that are dragging anchor and commercial vessels are coming into this anchorage for better protection. When we came here we put out 75 feet of chain, 5:1 scope. In these condition we need at least 7:1, but we are afraid to mess with it now since The wind is gusting and our anchor is holding. We set Drag Queen just in case.

We try to go back to sleep. Me in part of the bed that is dry and Fran in the aft cabin.

We get up at 5:30am and make coffee. We pull the anchor at 6:50am and we are underway to Marquesas. We are wallowing with the wind behind us and following seas.

George calls us on the radio and says they caught a tuna. We put out the trolling rods. At 8:30 we catch a 24″ cero mackerel. At 9:15 we catch a 21″ tuna.

Cero Mackerel
Cero Mackerel

George calls us on the VHF radio and suggests we go north of Half Moon Shoal since it might be calmer. It doesn’t seem to make much difference.

We approach the west side of Marquesas and we think it might be rough anchoring there. We decide to try anchoring on the northeast side of Marquesas. If that looks too rough we will anchor in Boca Grande Key.

It starts raining at 2:20. We have to close up the boat. With everything closed and our exhaust (annoying) fan not working it is really hot below and our refrigerator is not happy. The yellow light is blinking. According to the manual that means low voltage, but that doesn’t make sense because the batteries are fully charged from running the engine all day. We think it may be too hot so we try to cool it off with fans.

We get near the spot northeast of Marquesas and decide to continue to Boca Grande Key. The seas are really rough until we get into the Boca Grande Channel, then it calms way down. We raft up to Steel Lady.

The refrigerator is still not working. We think the problem is that it is next to the engine and is too hot. We open the engine room doors to cool off the engine room and now the entire boat is hot. We start the generator and run the A/C. The A/C pulls a lot of current and occasionally the generator goes into overload. When that happens we have to restart it, but eventually the boat cools down a little. The refrigerator is still not working.

In the meantime we clean fish. We filet three tunas, the one Fran caught and two from George and Nancy. We cut the cero mackerel into 1″ steaks. After that we clean up the blood and guts and freeze all the fish, except for enough cero mackerel for dinner.

We try running the refrigerator on 110 AC with the generator and surprisingly it works.

We grill some cero mackerel. It  is awesome.

We are on the edge of having cell phone service. It is Mothers Day and Fran gets texts from her children. She even talks on the phone, but the calls keep dropping.

We leave the generator running while we go to bed so the refrigerator will run until the generator runs out of gas. When we get in bed, the bit of breeze we have is blowing fumes into the boat, so we turn the generator off. The refrigerator has a cold plate and it should keep cool for a while.

We had a good day despite the weather and problems with the refrigerator. We caught fish and we are here in this awesome anchorage. You can down-load our track, track20170514.kmz and open it in Google Earth if you want to explore Boca Grande Key.