ACR 3947 SM-3 Lifebuoy Self-Igniting Marker Light
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The ACR SM-3 Lifebuoy Self-Igniting Marker Light 3947 is a SOLAS, MED and USCG-approved high-intensity LED strobe designed to mark a crew-overboard position. When released from its mounting bracket and turned upright, the built-in gravity switch automatically activates the strobe. The buoyant light self-rights in the water and provides 360-degree visibility for approximately two nautical miles, helping rescuers maintain visual contact with the incident location.
Key Features
- ACR product number: 3947
- Model: SM-3
- High-intensity LED crew-overboard marker strobe
- USCG, MED and SOLAS approved
- Automatic activation through an internal gravity switch
- Self-righting, buoyant design floats upright
- Provides 360-degree visibility for approximately two nautical miles
- Minimum light intensity of 3 candelas
- Flash rate of approximately 50–70 flashes per minute
- Operates for at least 40 hours at 30°C or 24 hours at -1°C
- UV-resistant polycarbonate housing in international safety orange
- Includes a mounting bracket with the same mounting-hole pattern as the earlier ACR SM-2 bracket
- Requires two user-replaceable AA Energizer L91 lithium batteries
- Batteries are not included
Intended Use
The SM-3 is intended for installation beside a lifebuoy or ring buoy as a crew-overboard position marker. It is suitable for commercial vessels, workboats, passenger vessels, cargo vessels, fishing vessels, tugs, offshore operations, charter boats, cruisers and other vessels requiring an approved self-igniting lifebuoy light.
Fitment and Approval Notice
Confirm the vessel’s applicable Transport Canada, USCG, SOLAS, flag-state and inspection requirements before installation. Mount the supplied bracket where the light remains secure in normal operation but can be released immediately with the associated lifebuoy during a crew-overboard emergency.
The light measures approximately 253 mm long by 56 mm in diameter. Its bracket uses the same mounting-hole pattern as the discontinued ACR SM-2, allowing many existing SM-2 installations to be upgraded without an additional adapter plate.
When This Product Needs Replacement
- The housing, lens or mounting bracket is cracked or damaged.
- The light does not activate reliably when turned upright.
- The strobe is weak, intermittent or fails its inspection test.
- The unit no longer self-rights or floats upright correctly.
- Battery contacts show corrosion or contamination.
- The approval markings or identification label are unreadable.
- The manufacturer or applicable marine authority requires replacement based on service age.
Installation Notes
- Install two AA Energizer L91 lithium batteries before placing the light in service.
- Observe the battery polarity markings inside the housing.
- Secure the light in the supplied bracket with the lamp end facing downward so it remains deactivated during storage.
- Position the bracket where the light can deploy with the associated lifebuoy without snagging on rails, lines or vessel equipment.
- Test the gravity-switch operation according to the ACR instructions and the vessel’s safety-equipment inspection schedule.
- Replace the batteries after emergency operation and whenever required by the inspection or battery-replacement schedule.
Alternate/Superseded Part Numbers
- Current product number: 3947
- Model designation: SM-3
- The SM-3 is the current replacement for the discontinued ACR SM-2 lifebuoy marker light.
- Previous SM-2 reference: 3940.1
Parts Desk Insight
The automatic function depends on the light being stored in the correct downward orientation and turning upright when deployed. Check the bracket position, battery condition and gravity-switch activation regularly rather than waiting until the vessel’s annual safety inspection. For compatible lifebuoys, mounting brackets and related safety equipment, see below.
- Lifebuoy Holder – Stainless Steel (Ring/Horseshoe & Light)
- Life Buoy Holder – Ring & Horseshoe Mounting Bracket
- LALIZAS Stainless Steel Horseshoe Lifebuoy Bracket with Light Base
- STELLA Lifebuoy LED Light – SOLAS
- Lifebuoy Light with Bracket L90 – SOLAS
- 30" Life Ring – 4.0 kg
- 30" Life Ring – 2.5 kg
- Lalizas Lifebuoy Ring Case Set
- Lifebuoy Ring Container – Wall-Mount Storage Box
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 3–4 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
We are serious about product integrity — and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.