By the Chase Leavitt service team · Portland & Ellsworth, ME · Updated November 2026

The short answer

If you can have only one, get an EPIRB. It’s vessel-registered, it transmits to satellites, and it covers the boat. The other two — PLBs and AIS man-overboard beacons — are person-worn and they’re useful, but they don’t replace the EPIRB.

EPIRB

Emergency Position Indicating Radio Beacon. Registered to the vessel. Transmits a 406 MHz distress signal to the SARSAT satellite system, which routes it to NOAA, which routes it to the Coast Guard, which dispatches a rescue. The system works. We know it works because we’ve talked to people it has rescued.

Two flavors:

• Cat I (float-free). Mounted in a hydrostatic release bracket. If the boat sinks, the bracket releases the EPIRB at depth and it floats to the surface and activates on its own.
• Cat II (manually deployed). Mounted somewhere accessible, deployed by a crew member who pulls it out and activates it.

Most commercial vessels run Cat I because regulations have been moving that direction. The Cat II is fine for recreational use as long as someone can get to it and activate it — which assumes you have time to. The point of Cat I is that it works whether or not anyone’s conscious.

PLB

Personal Locator Beacon. Same satellite system as the EPIRB, but person-registered and much smaller. Worn on a belt, in a pocket, or clipped inside a foul-weather jacket. Activates manually.

The PLB’s job is to get found if you’re separated from the vessel — overboard, stranded after an abandon-ship, or out hiking from a fishing camp. NOAA registers PLBs to a person, not a vessel. If you change your phone number, update the registration.

PLBs don’t last as long as EPIRBs. Battery life is rated 24+ hours of transmission, but battery replacement intervals are typically 5–7 years from manufacture. Battery service is sometimes specialized — call us before you buy a brand we don’t service.

AIS man-overboard beacon

This is the newest of the three. Personal AIS beacons (often integrated into PFDs) transmit a VHF AIS signal to nearby AIS-receiving vessels, including the boat you fell off of. The advantage: the response is local and fast. The disadvantage: it only works if there’s an AIS receiver close enough to hear it.

For sailing in busy waters — Long Island Sound, Boston Harbor, the Maine coast in summer — an AIS beacon is genuinely useful. For an offshore singlehanded crossing, it’s mostly hope: if the boat is sailing away on autopilot and there’s nobody else nearby, the AIS signal isn’t reaching anyone.

That’s why we recommend AIS as an addition to a PLB, not a replacement for it.

How to pick

The decision tree we walk people through at the counter:

• Commercial fishing vessel — EPIRB is required by 46 CFR 28. Get a Cat I. PLBs for each crew are an excellent addition.
• Inspected vessel under Subchapter T or K — same answer. EPIRB required. Crew PLBs strongly recommended.
• Offshore yacht — EPIRB required for ISAF-rated races; recommended otherwise.
• Coastal cruising yacht — EPIRB recommended. PLB on the captain. AIS optional but increasingly common.
• Day boat or charter — depends on the operating area. If you’re staying inside the Boundary Line, the regs are different.

Registering and updating

This is the most-missed step. NOAA registers all three types of beacons at beaconregistration.noaa.gov. The registration is free. The renewal is every two years.

What we see at the counter: people register the beacon when they buy it, then change their phone number two years later and never update the registration. When the beacon activates and the SARSAT signal is received, NOAA’s first action is to call the registered phone. If that phone is disconnected — or worse, belongs to a stranger — the rescue gets slower.

Update the registration when:

• You change your phone number
• You buy or sell the boat
• Your home address changes
• You replace the battery (some service shops update for you, some don’t)
• The two-year reminder email arrives

Battery dates and service

Every beacon has a battery replacement date printed on the case. EPIRBs are typically 5 or 10 years; PLBs typically 5–7 years; AIS beacons vary. Replace at or before the date.

Aftermarket batteries: just don’t. Manufacturer batteries are factory-spec for the antenna power output, and the cost difference is genuinely small relative to the device cost. We don’t install aftermarket batteries even when customers ask. Whatever pennies you save aren’t worth the risk that a non-spec battery underpowers the antenna and the satellite doesn’t pick up the signal.