Chart Plotter Shuts Off When Outboard Engine is Cranked Over

[mkelly]

Recently I purchased the Garmin 741 combo chart plotter and SONAR. I was nervous about going to touch screen in a boat. It's been great, but I think I have a wiring [problem]. I am not much good when it comes to electrical wiring and breakers.

[The GARMIN GPSMap 741] is currently run thru one of our space switches, which to me means it is direct-wired to the battery most, likely with an in line fuse I consistently have it running when at rest waiting for crab or shrimp pots to soak. Often when starting the motor, power is interrupted, and the unit shuts off. [This problem] can't be a good thing, and having to re-start is a pain. Judging from that condition, can anyone tell me how it's wired?

What I should do to make it more independent?

[Jefecinco]

Your battery charge level may be a bit low. If so, the battery voltage when the starter is engaged may become lower than the minimum threshold required to keep the Garmin running. This is a common problem when batteries become old or when the engine is operated at low speed for long periods and subjected to frequent starting.

I recommend you check your battery voltage while cranking the engine.

Butch

[jimh]

No one can know how your boat is wired from your description of the behavior of your chart plotter.

What is evident: the battery voltage is sagging too much during engine cranking.

The remedy: reduce the voltage sag in the engine cranking battery during engine starting.

To reduce the voltage sag in the engine cranking battery during engine starting:

--restore the battery to full charge

--install a battery with greater capacity to provide high current

--reduce any voltage drop in the power distribution wiring

[mkelly]

OK, that's very useful info. I believe the batteries are [contributing to the cause of the problem of the chart plotter shutting off].

[jimh]

The best solution to the very common problem of electronic devices on small boats being re-set or rebooted when the outboard engine is started is as follows:

--install a separate battery for use with the electronic devices on the boat

--isolate all electronic loads to the separate electronics battery

--install a dual alternator output circuit on your outboard engine (if available, typically available on Evinrude and Yamaha outboard engines) to charge the isolated battery

--if no dual alternator output is available, use an automatic combiner relay or voltage-sensitive relay (ACR or VSR) accessory to facilitate charging of the isolated electronics battery

--install a primary power distribution switch that permits for emergency parallel operation of the cranking battery and the electronics battery for engine starting in circumstances that warrant the two batteries in parallel.

[StormWarning]

As said above a bad battery could be the culprit. I had the same concern in a past boat that was not only when the motor turned over but also when I use my trim tabs. Turned out the end of my powercable was getting corroded. The corrosion can also cause a loss in voltage making the system less efficient. A new power and ground cable did the trick. It was a 10-AWG wire. Price was about the same so I replaced with a 8-AWG conductor which is [a larger wire that will have less voltage drop] but why not--unless the larger wire is really expensive. My voltage before the repair was about 12-Volts at the battery and was 0.3-Volts lower or about 11.7-Volts at the helm. Once repaired it was the same voltage at the helm as at the battery.

[jimh]

The voltage drop in a conductor that feeds a secondary power distribution panel from a primary power distribution source will typically not be affected by outboard engine starting currents because typically those currents do not flow through that conductor. In the problem being analyzed in this thread, the voltage drop that occurs is most likely to be at the battery terminal and caused by the battery being in a poor condition or in a reduced state of charge.

Current to operate the power trim and tilt system of an outboard flows through the same conductor as the electrical cranking motor current.

It would be very unusual that the power source for all electronic devices in a boat would be taken from the outboard engine electrical wiring harness. Typically the power for the helm is taken directly from the battery by its own conductor, as described above by StormWarning.