Boat Emergency Battery Starting: Understand Your Switch First
Justin HarrisonShare
A dead cranking battery can end a fishing trip. Before adding an emergency starting connection, identify your switch, battery banks and engine requirements. Similar-looking switches can have different internal connections, ratings and instructions.
Correction: Our earlier article confused a selector switch with a dual-circuit switch and included a wiring diagram that did not establish a suitable installation for every boat. That diagram and the universal wiring steps have been removed. RCO’s switches are not Blue Sea Systems branded products. Appearance alone does not establish equivalent performance or certification.
Featured image: A Blue Sea Systems-branded switch is shown for the manufacturer comparison below. It is not a photo establishing the identity or specifications of the unbranded switch sold by RCO.
Selector versus dual-circuit switches
- 1–2–BOTH–OFF selector: selects one of two banks or connects both to a common circuit, according to its actual wiring and instructions.
- OFF–ON–COMBINE dual-circuit switch: is a different arrangement intended to operate separate circuits and combine them when configured for that function.
- ON–OFF disconnect: opens or closes a circuit; it does not provide bank selection by itself.
For a documented manufacturer comparison, the genuine Blue Sea 6007 is a selector with 1, 2, BOTH and OFF positions. The genuine Blue Sea 6011 is a Dual Circuit Plus model with OFF, ON and COMBINE positions. These model descriptions apply to Blue Sea products, not automatically to an unbranded lookalike.
What to confirm before emergency starting
- Record the actual switch manufacturer and model. Obtain its terminal diagram, operating instructions and current ratings.
- Identify each bank’s voltage, battery chemistry and starting capability. Have the engine and battery manufacturers’ compatibility requirements checked.
- Have a qualified marine electrical installer determine the circuit layout, cable size, connection protection and charging arrangement for your boat.
- Ask the installer to label the switch and explain the normal and emergency operating positions for that installation.
Do not connect a 24V or 36V trolling bank to a 12V engine starting circuit. Selecting one battery from a series bank is not a universal workaround. Its connections and equipment requirements must be evaluated before any such arrangement is installed.
If the engine will not start
Use only the emergency starting procedure documented for your installed equipment. Do not improvise a connection based on switch appearance or this article. If you do not have a verified arrangement, use an engine-compatible starting aid according to its instructions or contact assistance.
Blue Sea’s published instructions warn against switching to OFF with the engine running. Check your own switch and engine instructions before changing switch positions. This article does not prescribe a switching sequence for an unidentified switch.
Mounting and customer examples
Browse our universal battery switch mounting brackets and Customer Installation Gallery to compare mounting locations. Photos show individual customer installations, not proof of electrical compatibility. A bracket organizes and supports a switch; it does not regulate voltage or filter electrical noise.
About the author: Justin Harrison, Rocket City Outdoors. Updated October 10, 2026. Manufacturer references below describe the named manufacturers’ equipment; they are not specifications for unbranded switches sold by RCO.
