On April 28, 2024, the yacht Flagship caught fire at a shipyard on the Miami River. The boat was uncrewed and docked. Security camera footage showed an explosion originating from the hatch above the space where the 24-volt lithium-ion battery bank was located. Firefighters eventually moved the vessel to a nearby seawall where they extinguished the fire. The Flagship sank at the seawall and was declared a total loss, valued at $5 million.
On January 9, 2025, the motor yacht Naisca IV caught fire while moored near Marseille. The fire, traced to a lithium-ion battery, destroyed the vessel and damaged two neighboring yachts.
These are not isolated incidents. The NTSB, the U.S. Coast Guard Research and Development Center, and marine insurers are all tracking a significant increase in lithium-related fires on recreational and commercial vessels. The U.S. Coast Guard issued a formal safety alert on lithium-ion battery system installations following a fire aboard an inspected passenger vessel. The pattern is consistent: the fire starts in a battery compartment, often while the vessel is uncrewed and docked, and the outcome ranges from serious damage to total loss.
If you own a larger boat with a lithium house battery bank, this is a conversation worth having before something goes wrong.
Two Separate Fire Risks on a Larger Inboard Vessel
It helps to think about fire protection on a larger boat in terms of two distinct risk zones, because they have different causes, different dynamics, and different protection needs.
The engine compartment. Inboard diesel engine compartments on cruisers, sportfishers, and motor yachts are well-sealed by design. NFPA 302 and ABYC standards require engine compartments on gasoline and diesel inboard vessels to be enclosed to prevent fuel vapors from migrating to the bilge and cabin. That enclosure is exactly what makes them suitable for automatic suppression.
The fire causes in inboard engine compartments are well documented: fuel line failures at fittings and hose connections, fuel that accumulates in the bilge and ignites from a spark, overheated turbochargers with accumulated oil residue nearby, hydraulic line failures on vessels with hydraulic steering and trim systems, and electrical faults in the dense wiring that runs through the engine space. A diesel engine running hard offshore generates sustained heat in a sealed space with multiple flammable fluid systems running through it.
The battery compartment. This is the newer and growing risk category. As boat owners upgrade from lead-acid house battery banks to lithium-ion systems for their weight savings, charging efficiency, and capacity, they are introducing a different fire risk profile into a space that was previously low risk.
Lithium battery fires in marine environments follow the same pattern documented in other applications. The fires usually start during charging, often while the vessel is unattended at a dock. The NTSB report on the Flagship noted the explosion originated below the hatch covering the battery bank space. The U.S. Coast Guard safety alert noted that an integrated lithium battery bank caught fire aboard an inspected passenger vessel. The cause in most documented cases involves a battery management system failure, overcharging from an incompatible charger or shore power issue, or a cell defect that develops into a thermal event over time.
The honest thing to say about lithium battery fires is the same thing that applies in every other context: once a battery cell has entered full thermal runaway, the self-sustaining chemical reaction cannot be stopped by any suppression system. The value of automatic suppression is early intervention before that threshold is reached, limiting the spread of fire from the battery compartment to the surrounding vessel before the situation becomes unrecoverable. On a boat, where you are surrounded by water and far from a fire department, early intervention is everything.
Why Being on the Water Makes This Worse
A boat fire is categorically different from a fire in a building or a vehicle on land. Help is not close. The fire department is not minutes away. Coast Guard response takes time. And the vessel itself, the thing that is on fire, is also what is keeping you afloat.
For fires that start while the vessel is docked and uncrewed, the outcome depends entirely on what is protecting the boat in the absence of any person who could respond. A fire that activates a dock fire alarm brings the marina attendant and eventually the fire department. By then, on a vessel with a lithium battery fire that has been developing for any significant time, the result is typically what happened to the Flagship.
An automatic suppression system inside the battery compartment responds to heat at the source, in the first seconds, without waiting for anyone. That response does not put out a full thermal runaway once it is underway. But it can intercept a developing heat event before the battery reaches that point, and it can limit the spread of fire to surrounding materials in the compartment and adjacent spaces even when it cannot stop the battery itself.
How BlazeCut Works on a Larger Vessel
The BlazeCut T Series is a pre-charged flexible tube that routes inside an enclosed compartment and responds to heat without any connection to the vessel's electrical system. No wiring, no power draw, no connection to the bilge blower system or any onboard electronics. The tube is both the heat sensor and the delivery mechanism for the FK-5-1-12 clean suppression agent inside it.
When temperature at any point along the tube reaches approximately 248 degrees Fahrenheit, the tube opens at the hottest spot and discharges FK-5-1-12 directly onto the fire source. It responds inside the protected compartment, at the source of the heat, in the first seconds.
FK-5-1-12 is a clean gaseous agent. It is non-conductive, non-corrosive, and leaves no residue. In a marine environment where a dry powder or water-based discharge would cause its own damage to electrical systems, engines, and instrumentation, FK-5-1-12 suppresses the fire and dissipates cleanly.
Battery compartments are the strongest application on larger vessels. A dedicated lithium battery bank compartment is typically a well-defined enclosed space that a BlazeCut tube is sized to protect. A smaller battery compartment of roughly 24 inches by 18 inches by 14 inches has a gross volume of approximately 3.5 cubic feet, netting around 2.3 cubic feet after the battery banks and racks are accounted for. A TR200FK covers that range. A larger battery compartment of roughly 36 inches by 24 inches by 18 inches has a gross volume of approximately 9 cubic feet, netting around 5.9 cubic feet. A TR400FK is the right starting point there, and depending on the layout two tubes covering separate zones may be worth considering.
To calculate the right tube for your specific battery compartment: measure the interior dimensions in inches, multiply length x width x height, divide by 1,728 to convert to cubic feet, subtract roughly 35 percent for the battery banks and mounting hardware inside, and match the net volume to the sizing guide on the product pages.
Engine compartments on inboard vessels are larger and more complex. A single inboard engine bay on a 28 to 35 foot cruiser typically has a gross interior volume of around 30 cubic feet and a net open volume after the engine and components of around 16 cubic feet. A twin engine bay on a larger sportfisher or cruiser is significantly larger still.
A single BlazeCut tube cannot protect a space this large. For engine compartments, the right approach is either multiple tubes covering separate high-risk zones within the space, or a single tube routed specifically in the zone of highest fire risk, near the fuel system, the fuel filters, the injection system, and the exhaust manifold area. This targeted approach provides meaningful protection at the most likely ignition points without overclaiming full compartment coverage.
The sizing guide on the product pages and the contact form at Modern Fire Suppression can help you think through the right routing and tube selection for your specific vessel layout. For complex or large engine compartments, reaching out before ordering is worth the time.
The Uncrewed Docked Vessel Problem
The Flagship fire, the Naisca IV fire, and most of the lithium battery boat fires documented in the past few years have one thing in common: the vessel was uncrewed when the fire started. The boat was at the dock, nobody was aboard, and by the time anyone responded the situation was already serious.
This is the scenario that automatic suppression is specifically built for. It does not require a person to be present. It does not require anyone to notice smoke or smell something. It responds to heat inside the compartment, at the source, without any human involvement.
For a vessel that spends significant time at the dock with the battery bank on charge and nobody aboard, automatic suppression inside the battery compartment is the only protection that addresses the gap between when a thermal event starts and when any person could realistically respond.
FAQ: Inboard Boat Fire Suppression
Can BlazeCut stop a lithium battery thermal runaway once it has started? No. Once a lithium battery cell has entered full thermal runaway, the self-sustaining chemical reaction cannot be stopped by any suppression system. What automatic suppression inside the battery compartment provides is early-stage heat intervention, limiting the spread of fire from the battery to surrounding compartments and materials before the situation becomes unrecoverable. That early window is where the protection lies.
Is FK-5-1-12 safe for marine electronics, wiring, and engine components? Yes. FK-5-1-12 is non-conductive, non-corrosive, and leaves no residue. It is safe for electrical systems, wiring, instrumentation, and engine components. After a discharge, ventilate the compartment and assess for fire damage before operating the vessel.
Can a single BlazeCut tube protect my entire engine compartment? Not for most inboard engine compartments on boats 28 feet and larger. These spaces are typically too large for a single tube to cover comprehensively. The practical approach is either multiple tubes covering separate high-risk zones, or a single tube routed specifically near the highest-risk areas, the fuel system, injection system, and exhaust manifold area. Reach out before ordering to discuss the right approach for your specific vessel.
What size tube do I need for my battery compartment? Measure the interior of the battery compartment in inches, multiply length x width x height, divide by 1,728 to get cubic feet, subtract roughly 35 percent for the battery banks and hardware inside, and match the net volume to the sizing guide on the product pages. A smaller battery compartment in the 2 to 3 cubic foot net range needs a TR200FK. A larger compartment in the 5 to 6 cubic foot net range needs a TR400FK.
Does the system work when the vessel is docked and uncrewed? Yes. The BlazeCut T Series requires no power and has no connection to the vessel's electrical system. It responds to heat through the physical properties of the tube material and is active whether the vessel is underway, at anchor, or docked with nobody aboard.
Does the system need to be wired into the vessel's bilge blower or alarm system? No. The standard BlazeCut T Series operates entirely passively. For vessels where a discharge notification is needed, the ES model tubes include an integrated pressure switch that can trigger a beacon, sounder, or relay at the moment of discharge. Contact Modern Fire Suppression to discuss whether the ES model is appropriate for your installation.
What happens after the system discharges? Do not enter the compartment immediately after discharge. Wait for the agent to fully disperse, then ventilate before inspecting. Assess the compartment for fire damage, have any lithium batteries involved inspected by a qualified technician before charging again, and replace the BlazeCut tube before the vessel returns to service. Replacement tubes are available directly through Modern Fire Suppression.
Protect the Vessel at the Dock and Underway
BlazeCut T Series systems for battery compartments and engine compartment zones are available at Modern Fire Suppression. The sizing guide on the product pages walks through the calculation for battery compartments. For engine compartments or complex layouts on larger vessels, reach out through the contact page before ordering and someone can help you figure out the right configuration for your specific boat.