The luxury of onboard electronics and electrical devices cuts both ways. What it gives in terms of convenience, it takes in terms of a load on your battery bank that needs recharging. There is tons of good info available on the net and in books on sailboat electrical systems. I especially like Sailboat Electrics Simplified by Don Casey. The information is concise and clearly presented in a way that makes it easy to refer to when I’ve forgotten some important point. I won’t bore you by rehashing all that but cut right to what I did and why.
Summer Dance has a single group 24 deep cycle battery so far. With the addition of accessories like the music system, the LED strip lights, and the autopilot, a single battery charge became insufficient for a two-day cruising weekend, let alone those occasional great three-day weekends. I needed to find a way to put some amp hours back into the battery while we were out on the water. I don’t need a weekday system to charge the battery while the boat sits in a slip. We trailer to every launch and home again and I have an onboard charger for that already.
At first, I considered a solar panel. But after seeing the cost and complexity of a quality system and how little charge we could expect, especially at the northern latitudes where we sail, the return on investment looked bleak and my focus turned to our outboard motor. The winds are usually light in the North Idaho lakes in summer and we typically spend a lot of time motor sailing, more than I’d like, actually.
The good news is that our outboard motor, an 8HP Yamaha 4-cycle (model F8MLHC), already had generator coils. All it needed was a regulator/rectifier to convert the unregulated AC output into regulated DC current suitable for the battery. The manual states that the output is 80 watts maximum, or 10 amps at 12 volts DC.
If your outboard motor doesn’t have generator coils installed and you would rather consider a solar panel solution, check out Solar panels for boats: an easy installation guide.
Get a charge out of your outboard
So I turned to eBay (where else?) and bought a used regulator/rectifier (Yamaha part no. 68T-81960-00-00). I had it mounted in 5 minutes and connected to the engine as shown in this diagram. The last step was to connect it to the battery onboard.
My goal for the onboard wiring was to be able to easily connect and disconnect the motor for trailering with a heavy-duty waterproof connector. I wanted the process to be as simple as connecting the fuel line. But I didn’t want to mount a cable connector in the hull that required drilling another hole.
At the motor, I made a short wiring harness out of 12 AWG cable. It connects to the rectifier/regulator output and to ground on the motor, exits the motor at the front grommet and terminates in the male half of a 2-pole Delphi Packard Weatherpack connector.
In the boat, I ran a 12 AWG duplex cable from the battery along the bottom of the port side of the cockpit sole to the aft vent fitting. I ran the wiring right inside the short vent hose and out the scoop with enough cable to reach the outboard motor where I crimped on the female half of the connector. I covered all exposed cables with flame-retardant woven loom. When disconnected, the boat cable folds neatly out of the way along with the gas line. I spliced a 10 amp fuse holder on the battery end of the positive wire and connected it to the battery’s positive terminal. The negative wire is connected to the negative bus bar nearby.
The proof is in the put-putting
At cruising throttle, the motor puts out 2-3 amps to the battery, more than enough to offset the autopilot, GPS, and music system that are typically on at the same time. At full throttle, the battery gets a 5 amp charge.
I’ve been using this setup for two years and I haven’t even had a low charge condition yet. I’m glad that we don’t have a big clumsy solar panel hanging off the stern. We might need one someday for week-long cruises, but even then it will be nice to know that we have more than one charging option.
The bottom line:
Suggested price: $120.25 + installation
$tingy Sailor cost: $71.05 installed
Savings: $76.40 + installation
What do you like most about your outboard charging circuit or solar panel?