Went out yesterday with Scott Leon (Paradigm Shift Charters) on Toy Boat 2, looking for tuna, yellowtail and dorado. I wanted to test out a couple of short offshore fly rods from Sea Level Fly Fishing for our sister site, Beyond The Breakwater.

Well, the fishing was slow, other than this 135lb marlin that hit one of our tuna spreader bars. The fish was roughly 10ft. long, including the bill. My second marlin ever, and my first local fish, from my own boat, too!

Kudos to Scott, who drove the boat and leadered the fish. I mostly cranked and kept my fingers crossed.

On the negative side, both of our batteries went dead, despite the engine running most of the time. We discovered this after we stopped the engines to fish a kelp paddy, and couldn't get the motor going again. We were lucky in that after letting the batteries rest for a few minutes, we were able to scrape out enough juice to turn the E-TEC over once or twice, and the engine started right up. Of course, the motor did not get turned off until after we got back to port...

At first, my initial suspicion was that there must be a significant short somewhere in the system. After all, what are the odds that both batteries would be dead, especially with our nifty battery combiner setup?

In order to have drained the batteries with the engine running, the short would have had to have been pulling a lot of amps from both batteries, and/or both batteries would have to have been damaged and unable to hold a charge. However, none of the circuit breakers tripped, and there was no sign of smoke or overheated circuits.

I was pretty sure the batteries were OK, as I had load tested both batteries a few month earlier, and they checked out fine. After I got home, I recharged the batteries, and load tested again. They were still OK.

This left the battery combiner as the only thing (other than the on-board charger) that was connected to both batteries and ground. It did not appear scorched or overheated, but I pulled it out, just in case.

Then I checked the alternator output from the E-TEC. After all, with 25 amps of capacity, it should have been more than capable of keeping everything charged and running. So I pulled the boat out into the driveway, hooked it up to a hose and started the motor. When I put the multi-meter on the engine lugs in the transom, it said that the alternator was outputing 12.6V. This seemed a bit low, but not unreasonable.

After a couple of phone calls to both BRP and our local Evinrude dealer, I was advised that only way to be sure about the alternator was to drain the battery below 12V, run the motor, and check both the output voltage and current.

How do you check the current running through the battery cables? You can use a device called a clamp meter. It uses induction to allow you to monitor the current going through an unpaired wire. I bought the MA220 from Extech, for under $100 on the Internet.

I left the lights and other electronics on until the battery was drawn down below 12V (the MA220 can also function as a simple multi-meter, it said 11.5V), and started the engine again. Actually, since a 12V battery with only 11.5V of output is almost dead, I had to put the other battery on-line in order to get enough juice to start the engine.

After it started, I switched the second battery off, and used the clamp meter to measure the alternator current and voltage output. The alternator output voltage now read 11.3V, and only 1.6 amps of output! Under these conditions, the engine should have been putting out the full 25 amp capacity of the alternator, at something over 12V. I took the engine out of gear, and throttled up to 1,200 rpm, with no change in output.

So....back in to the shop! I still think the battery combiner is involved in some way, as there is no way both batteries could have been depleted at the same time without something connecting them both shorting out. Perhaps the battery combiner failure also damaged the engine charging system?

Boat Depot is taking me this next Tuesday, with the intent of getting the boat back to me Wednesday afternoon. Got to get that last tuna trip in before the Winter rains come!