Sierra RK40870 On-Off-On Rocker Switch SPDT

The Sierra RK40870 is a compact rocker switch built for the kind of panel work that never seems to have enough room. It's an On-Off-On design, which means you get a center off position and two live positions from one switch. That's handy when you want a single control to run something in two directions or pick between two circuits, and you don't want to give up half your dash to do it.

Let's talk about what On-Off-On actually gives you. Electrically, this is a single pole double throw switch, SPDT for short. One common terminal feeds two outputs, and the center detent breaks the circuit entirely. Flip it up and the common connects one way. Flip it down and it connects the other. Park it in the middle and everything's off. So on a boat, that's the switch you reach for when you've got a reversible load or a choice to make. Think trim up and trim down. A blower on a manual override or off. Two lighting circuits off one control. It does the job of what would otherwise take two separate switches.

One thing worth knowing when you wire it. Because the center is off, you don't need a separate kill switch for whatever it controls. The switch itself is the off. That keeps your panel simpler and your wiring shorter. Just remember which way is which when you land your wires, and label the switch so the next person at the helm, maybe you on a dark night, isn't guessing.

The contacts are rated for 12 amps at 125 volts AC and 10 amps at 250 volts AC. Those are the published numbers, so size your circuit against them and don't push a switch past its rating. On most boats you'll be switching lower-current accessory loads, and this handles that comfortably. If you're running something with a heavy inrush, like a motor or a pump, factor that in and protect the circuit with the right fuse or breaker ahead of the switch. That's just good practice on any helm.

Install is straightforward if you've wired a rocker before. It drops into a standard rectangular cutout, and the rectangular body sits flush against the panel for a clean look at the dash. Before you drill, confirm the cutout against the switch itself so you get a snug fit, because a sloppy hole lets the switch rattle and lets water find its way behind the panel. Run your wires to the terminals on the back, keep your connections tight and sealed, and you're set. The high-profile rocker has a crisp, positive feel that's easy to find and flip by touch, and the black finish blends into just about any panel so it won't stick out next to your other controls.

Sierra builds this stuff for the marine world, so it's meant to live in a place that's damp, salty, and always moving. That said, our data doesn't list a specific waterproof rating on this one, so we'd treat it as a panel switch for a reasonably protected spot, behind a helm or inside a console, rather than something you leave fully exposed to spray. If you need a sealed, weatherproof switch for an open location, that's a different animal and we're happy to point you to one.

Here's the honest take. This isn't a fancy switch and it doesn't try to be. It's a well-made, no-nonsense On-Off-On rocker from a brand that's been supplying marine parts for decades. If you're building or repairing a panel and you need a reliable two-way control that fits a tight space, the RK40870 is an easy call. And at this price, it's the kind of part worth keeping a spare of in the boat's parts box. You'll use it eventually.