MasterCraft Battery Switch Tips | Your Boating Made Easier

Posted by Fuel Media Inc on January 21, 2016@ 08:44pm

MasterCraft builds an amazingly well engineered boat. From time to time though we have owners talk about issues they experience. One of them is dead batteries and other times it is just “odd” behaviour from electronics. Here is a little “tutorial” that MasterCraft put together to help improve your boating enjoyment and reduce your chance of being stranded.

Some customers are experiencing odd behavior with their displays and other electronic
components in “COMBINE BATTERIES” position. This is typically
due to low battery voltage on both the start and house batteries.


Boats built since 2008 that are equipped with dual batteries come with a VSR (Voltage
Sensitive Relay) circuit. The battery switch has 3 positions: OFF, ON, and COMBINE

  • With the battery switch in the OFF position, there is only power to the bilge pump (and stereo memory for 2013MY).
  • With the battery switch in the ON position, all accessories receive power from the HOUSE battery.
  • With the battery switch in the COMBINE BATTERIES position, emergency power from the START battery is added in order to start the boat.
  • The VSR prioritizes charging power from the alternator to the batteries.
  • When the battery switch is in the ON position, the VS directs power to ensure that the START battery is fully charged before charging the HOUSE battery.
  • When the VSR is left in the COMBINE BATTERIES position, it alternates charging between the START and HOUSE batteries.
  • Alternator output for recharging is a function of engine rpm. Max alternator output is not achieved until 3500 rpm.


The ONLY time a battery switch should be placed into “COMBINE BATTERIES” position is when the start battery is dead. After the boat is running, it is best to move the switch to the “ON” position. This will ensure that the START battery is fully charged first so that consumers will not be stranded on the water. After placing the switch in ON position, running the engine at higher RPMs will shorten recharging time. In addition, turning off all non-essential accessories such as the heater or radio will shorten
recharging time.

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