Fire! Lost my Beneteau. Cause?!?

[Pat Ross]

Originally Posted by Captain Scott

It was a sad day earlier this year when my Beneteau 43 caught fire and sank.

Bummer - Condolences and Congrats on the escape, I have done that one, no easy feat


Pat

[Lake-Effect]

Originally Posted by Exile

A bit off-topic but wondering what others think, and what ABYC might have to say about inline fusing in otherwise properly fused circuits. Sorry to hear about the OP's loss and hope he can get to the bottom of it.

(well, Hiii! )

The ABYC DC fuse/breaker specs are primarily about protecting the wiring, not the device. When you have battery banks able to dump 100s of Amps into wiring, even heavy wiring will burn up in a dead short. So DC fuses/breakers are as near to the power source (battery, panel) as possible, and sized to protect the wire they feed.

A special case is some DC motors, the biggest example being bilge pumps. Certain conditions (locked rotor, or blocked outlet) will cause the current to increase through the motor, heating it up, but not enough to blow the typical panel fuse or breaker.

The manufacturer of these pumps etc will specify the inline fuse size that will blow on this elevated current; and they may even provide the inline fuse-holder and fuse with the pump.

Other devices - eg VHF or automotive marine stereo often have inline fuseholders as well. presumably for enhanced protection of the device.

And also: if you have a "trunk" or bus situation, like a cabin-lighting circuit, and you want to tap in a smaller-gauge extension (eg a run to power some LED lighting in the V-berth), then you should have an inline or other fuse sized to protect the smaller-gauge extension, at the point where it taps into the trunk.

(I haven't done a NMEA2000 install; does that specify like a 5A fuse at the point where 12v is fed into the backbone?)

These are the only situations I'm aware of where you might see inline fusing in addition to the panel overcurrent protection.

[Exile]

Originally Posted by Lake-Effect

(well, Hiii! )

The ABYC DC fuse/breaker specs are primarily about protecting the wiring, not the device. When you have battery banks able to dump 100s of Amps into wiring, even heavy wiring will burn up in a dead short. So DC fuses/breakers are as near to the power source (battery, panel) as possible, and sized to protect the wire they feed.

A special case is some DC motors, the biggest example being bilge pumps. Certain conditions (locked rotor, or blocked outlet) will cause the current to increase through the motor, heating it up, but not enough to blow the typical panel fuse or breaker.

The manufacturer of these pumps etc will specify the inline fuse size that will blow on this elevated current; and they may even provide the inline fuse-holder and fuse with the pump.

Other devices - eg VHF or automotive marine stereo often have inline fuseholders as well. presumably for enhanced protection of the device.

And also: if you have a "trunk" or bus situation, like a cabin-lighting circuit, and you want to tap in a smaller-gauge extension (eg a run to power some LED lighting in the V-berth), then you should have an inline or other fuse sized to protect the smaller-gauge extension, at the point where it taps into the trunk.

(I haven't done a NMEA2000 install; does that specify like a 5A fuse at the point where 12v is fed into the backbone?)

These are the only situations I'm aware of where you might see inline fusing in addition to the panel overcurrent protection.

Most helpful -- thanks!!

Yes, there are a number of devices I can think of on my boat which have their own fuses. Otherwise it sounds like the few inline fuses I've installed are probably for naught.

I haven't done a NMEA 2K install either -- thus far I haven't had any need to replace my NMEA 0183 (is there?). My recent chart plotter upgrade just amounts to a ruggedized PC with a couple of waterproof monitors (Argonaut). Radar is standalone (Furuno). 0183 is tapped into everything but redundant to separate, standalone instruments. Not a huge fan of the marine consumer electronics world with its obsolescence & other issues, but really fun to check out on other peoples' boats! To each his own.

[Redline452]

I had an issue on my Jeanneau where a wire passing through a cable clamp on the engine block started melting through because someone post-factory used the bolt of the clamp as a negative terminal, which started heating up due to a poor connection. The clamp heated up and one of the wires was in the starter circuit which is not fused.

[Statistical]

Originally Posted by Lake-Effect

(well, Hiii! )
(I haven't done a NMEA2000 install; does that specify like a 5A fuse at the point where 12v is fed into the backbone?)

It does need OCP but it doesn't have to be an inline fuse at the backbone. Ideally it would be protected by a fuse or a circuit breaker right at the power source (panel board or busbar) to protect the power cable as well.

[gordonhinds]

We had as electrical fire while on board on a mooring. I saw what I thought was mist blowing past the cabin (I was inside). I went out to look and opened the anchor well which was full of smoke. For some reason I figured it was an electrical fire (I think it stank if burning plastic), raced back inside the cabin and turned off the battery switches, opened the hatches as the smoke was now in the forecabin and the fire stopped.
We had just had a lot of electrical work done including a new anchor windlass (not being used). Somehow the brand new anchor windlass (eight months old) shorted out. As it transpired the windlass had no fuse nor any circuit breaker.

The theory is that a small latent current went to motor on the windlass and over time created a short as the waxed coil melted. Once it shorted the full load of the battery discharged and the wiring loom caught fire and started burning back to the battery. Our boat is timber (cold molded so glued) and would have caught fire very quickly.

Electrical fires are super scary. We still have live wires in the boat as I slowly get rid of redundant wiring left randomly by lazy electricians.

Your fire is a mystery - new bilge pump is a clue. Somehow a heat source was created - the motor was on and I guess house batteries. What’s the main being hoisted with an electric winch? It could be the autohelm, even if it was off…

[DumnMad]

[QUOTE=Captain Scott;3782570](the boat had just come out of the yard and the only electrical work was the replacement of a bilge pump)

My first thought - could the time on the hard have pushed the hull out of shape and engine mounts out of alignment so that the cutlass bearing overheated??

[rslifkin]

[QUOTE=DumnMad;3785074]

Originally Posted by Captain Scott

(the boat had just come out of the yard and the only electrical work was the replacement of a bilge pump)

My first thought - could the time on the hard have pushed the hull out of shape and engine mounts out of alignment so that the cutlass bearing overheated??

I'd be shocked if you could get a shaft bearing of any kind hot enough to set the boat on fire without any obvious symptoms appearing first.

[DerekL]

Much has been said about an electrical cause but I would be suspicious of the running engine. If the salt water inlet was closed, in an indirect cooled engine, the heat would be dumped into the hot water system and for at least 20 minutes the engine itself would not overheat BUT the exhaust elbow where the rubber exhaust hose connects to the manifold is cooled by the salt water spray as it is injected into the exhaust to be blown out with the exhaust gases. If the salt water is off or blocked this doesn't happen and this elbow can overheat very quickly. It can get hot enough to destroy the hose and melt any plastic exhaust components like water separators and depending on what is in the vicinity could be the seat of the fire.


It is not unusual to get lifeboat call-outs to boats on fire to find that the above is the cause and has produced a lot of smoke but not always flames.

[tkalfaoglu]

Just wanted to say that I'm very sorry to hear of your loss, but very glad that you were all able to get out before it sank. I hope you find out what happened to your boat...

[mdenize]

Originally Posted by DerekL

Much has been said about an electrical cause but I would be suspicious of the running engine. If the salt water inlet was closed, in an indirect cooled engine, the heat would be dumped into the hot water system and for at least 20 minutes the engine itself would not overheat BUT the exhaust elbow where the rubber exhaust hose connects to the manifold is cooled by the salt water spray as it is injected into the exhaust to be blown out with the exhaust gases. If the salt water is off or blocked this doesn't happen and this elbow can overheat very quickly. It can get hot enough to destroy the hose and melt any plastic exhaust components like water separators and depending on what is in the vicinity could be the seat of the fire.
It is not unusual to get lifeboat call-outs to boats on fire to find that the above is the cause and has produced a lot of smoke but not always flames.

I agree the exhaust system is a very likely cause if the engine was on? I looked back over the post and that seemed likely unless I missed that. I was on a power boat that idled out of the mooring with the sea cocks closed and the sign not on the helm (skippers brain fade) any way I smelt burning fibreglass within 2nm and we shut the engines down and found smoke but no fire from the fibreglass mufflers. The stbd one was leaking from a rubber gasket under the water line. If he has spooled up the engine we would have had much bigger problem for sure. Salt water cooling is the only thing that stops a fire on boats with that sort of exhaust

[OneBoatman]

Yes to spontaneous combustion if you had hydrocarbon soaked rags. I'm thinking that the source of fire such as those which serve your instruments at your helm, a chartplotter. These are taken around tight bends as typically routed up pedestal supports and these were likely on since you were underway. So, a short is one possibility but not the most likely since the wires are normally fused and in series with a breaker. I am not against putting in good waterproof in line fuses in the circuit feed the instruments. All manufactures I am familiar with recommend this in their install instructions. Usually fed in parallel to either a single or sometime two separate breakers on the DC master panel. I have powered my instruments this way for over thirty years on two different vessels and fortunately have not had any fires. If you picked a plastic bag which completely starved your sea water intake your raw water impeller would disintegrate and your exhaust would then be direct from a starved mixing elbow possibly melting the water lift, if plastic, and exhaust hoses. Yet, a high temp alarm or engine room temp alarm should have been heard. This actually happens quite fast and is more common. Once plastic or hoses start to melt both are hot enough to ignite whatever other combustibles may be nearby, such as dinghy gas or diesel fuel. The smoke would of course be black. Such a terrible loss but it sounds like you did all the right things once discovered.

[tweitz]

Since you mentioned you were towing a dinghy, was there gasoline stored on board or could there recently have been a gasoline spill?