OFF-1-BOTH-2 Marine Battery Selector Switch Three Stud 32V DC Marine Battery Isolator Switch

Most people buy a selector to switch between two batteries. The MT134 also earns its keep as a diagnostic tool: with OFF-1-BOTH-2 positions on a single dial, you can run each bank on its own under load and find out which one is tired before it strands you.

Electrically it is a workhorse — 350A continuous, 600A intermittent and 1,200A cranking at DC 32V — with three studs, a copper contact bridge and a sealed ABS body. Two banks in, one common output out, and a dial that tells you where you are.

1. Start on position 1 — Run the boat as normal with the dial on bank 1. Watch the voltmeter through a loaded period rather than at idle.
2. Switch only after shutdown — Kill the engine or charger, move to 2, restart, and repeat the same loaded observation on bank 2.
3. Compare the two readings — A bank that sags noticeably further under the same load is the one to load-test properly. The selector has told you where to look.
4. Use BOTH to check charging — With the engine running and the dial in BOTH, both banks should climb together. If one stays flat, the problem is the cable or the battery, not the switch.

• One part number across the fleet — A workshop that stocks one selector covers every twin-bank boat in the yard, and a technician only has to learn one wiring layout.
• One spare on the shelf — A single spare unit covers every installation, which is usually the difference between a same-day fix and a lost weekend.
• Three studs, the same layout — Bank 1, bank 2 and common output are always in the same order, so a replacement is a like-for-like swap rather than a rewire.
• Copper bridge inside — Lower resistance than plated steel keeps the studs cooler at 350A and leaves a contact face that still cleans up after years of service.

• Check the hole before ordering — The barrel and fixing pattern must match the old unit. Measure the existing cut-out rather than the new switch.
• Photograph the old wiring — Three cables look obvious until one of them is a charger feed. Take a picture before anything is disconnected.
• Replace the lugs, not just the nuts — A selector is often changed because a joint failed. Fit new closed ring lugs while the cables are off.
• Fuse each bank separately — Two fuses at the battery ends protect both cable runs; the selector itself protects nothing.

MT134, OFF-1-BOTH-2 selector, DC 32V maximum, 350A continuous, 600A intermittent and 1,200A cranking, three studs. There is no minimum order quantity: single units, samples and mixed containers are all accepted, with pricing quoted against quantity and packing. Standard production takes 30 days from deposit, T/T or Western Union, 30% down and the balance before shipment. Carton packed; pallet lots quoted separately.

No. Shut the engine or charger down before moving the dial. Breaking a loaded DC circuit draws an arc and can damage an alternator.

Yes, when a single alternator or charger is running. Do not leave the dial there permanently, because a weak bank will pull the good one down.

Check the thruster's own duty cycle. The 600A intermittent rating covers short bursts, but the continuous total on the circuit must stay under 350A.

No. DC 32V is the maximum, which suits 24V nominal systems with charging headroom.

No MOQ on the MT134. Single units, samples and mixed containers are accepted, priced against quantity and packing.

Send your bank sizes, panel cut-out and cable size and we will confirm the MT134 configuration, packing and freight. No minimum quantity required.