Ask Sail: Wilting waypoints

“Starting my engine often wipes out some waypoints in my charting program. My multimeter tells me that the voltage to the charting system drops only .5 volt when the starter is cranking, but that seems to be enough to cause the problem. Everything else still works fine with the lower voltage. Any ideas?”

Janet Margelli, Marina del Rey, California

Gordon West replies: The problem is not the voltage, but rather spikes from the starter motor that creep into your charting system’s microprocessor and cause some of the circuits to momentarily stumble. If you could see the voltage feeding into your charting system with an oscilloscope, you’d see a forest of pulses when you press the starter button. What you need is a buffer battery that will keep these starter-motor spikes from reaching the electronics. Newmar’s Start Guard, for example, switches electronics to an internal battery system whenever the engine is cranking and, once the engine is running, recharges the buffer battery. It’s available at most marine electronics stores, or you can click on communication products/installation accessories at

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