Engine Fire - what is the likelihood?

[Ricd]

A well-maintained and run boat is very unlikely to sink. Do you carry a liferaft?

Yes I carry one but many things can cause the boat to sink irrespective of how well maintained it is: bad seamanship by me or of others, being caught out in weather, hitting stuff in the water (Vauxhall Corsa) etc..The likelihood of falling overboard at anytime is much greater than an engine fire but I do not always wear a life jacket or harness myself on. Many bad things can happen when when we go to sea in boats, most of them pretty severe.

 

[Deleted member 36384]

...... (3). So why fit one?

As you are calculating probabilities then you need to calculate the risked cost of the event which is the probability x times the cost of the event. If the mitigation cost is less than the risk cost you pay for mitigation. This means that events which have high value consequences but low probabilities of happening are usually protected by some low cost mitigation. An every day example is fire insurance for your home most people take this out because they could not recover from the financial loss easily.

If your boat is only worth £1000 and a probability of 1% of an engine room fire occurring then 0.01 x 1000 = £10. As the cost of a 1 kg fire extinguisher is £90, then I wouldn't buy one.

However, if the cost of consequence includes loss of life and future loss of earnings for a family then assume 20 years of loss of earnings at £30k per year then the risked cost is (0.001 x 20 x 30000) + 10 = £610, then its worth fitting an engine room fire extinguisher.

The above is of course subjective and simple, but at the end of the day, its one way of deciding the cost benefit of mitigation to prevent consequences.

 

[Ricd]

As you are calculating probabilities then you need to calculate the risked cost of the event which is the probability x times the cost of the event. If the mitigation cost is less than the risk cost you pay for mitigation. This means that events which have high value consequences but low probabilities of happening are usually protected by some low cost mitigation. An every day example is fire insurance for your home most people take this out because they could not recover from the financial loss easily.

If your boat is only worth £1000 and a probability of 1% of an engine room fire occurring then 0.01 x 1000 = £10. As the cost of a 1 kg fire extinguisher is £90, then I wouldn't buy one.

However, if the cost of consequence includes loss of life and future loss of earnings for a family then assume 20 years of loss of earnings at £30k per year then the risked cost is (0.001 x 20 x 30000) + 10 = £610, then its worth fitting an engine room fire extinguisher.

The above is of course subjective and simple, but at the end of the day, its one way of deciding the cost benefit of mitigation to prevent consequences.

Cost of boat is fully mitigated via insurance. Cost of life is another thing altogether so I have life jackets, flares, life raft, fog horn, fire blanket etc., which I deploy to manage the specific situations where on balance I feel there might be a risk to life and minimise it in those situations. I minimise the risk of engine fire through timely and proper maintenance of engine and all electrics to the point where I feel the likelihood (probability) of an engine fire is extremely unlikely (probably much less than 1 in a 100,000). It adds little further protection to fit a fire extinguisher to mitigate the consequences of an extremely unlikely risk.

 

[Salty John]

If you don't have an engine room extinguisher it's a good idea to have a hole into the engine compartment through which you can shoot a fire extinguisher.

I had an engine room fire caused when the alternator controller burst into flames as a result of a lightning strike. I put the fire out with two powder extinguishers. Quite a mess afterwards!

 

[pyrojames]

Which is to say: not very likely at all.

Electrical faults no more likely to cause a fire in the engine bay than anywhere else.
Oil leak onto turbo; not many boats have a turbo.
Coolant leak onto turbo; not many boats have flammable coolant!
Catastrophic engine failure; I don't see why that is likely to cause a fire. It tends to be prevalent in racing cars (Martin Brundle, McLaren-Peugeot, Silverstone springs to mind) but racing cars have red hot exhausts. Boats have very cool exhausts.

Not very likely but I have investigated engine fires caused by all of the above (cars, boats, trucks, ships). I don't have a turbo, and I don't currently have any auto fire suppression, but I plan to fit it.

More vibration, higher currents and more wiring in an engine bay, hence greater fire risk.
If you don’t have a turbo then you have a much lower risk.
If you have the prescribed quantity of ethylene glycol in your coolant, you might be surprised how flammable it can be! FP 110, Exp Limits 3.2-15%
Catastrophic engine failures, ie bearing failures, are usually accompanied by molten metal in a oil filled crankcase. If you have a conrod break, it occasionally comes through the side of the block, accompanied by oil and hot stuff. Cue explosion/fire.

 

[davidej]

. A manual system might have some attraction, though.

The common way of accomplishing this is to have a small hole (with a cover you can slide away) in a suitable place -usually the companionway - to insert a manual fire extinguisher

 

[alant]

Thinking of installing an auto fire extinguisher in engine compartment. Doing a risk assessment I know the consequences of a fire at sea is severe but what is the likelihood of a modern marine diesel engine of catching fire? What might cause a fire in the engine?

I've had two 'engine fires'.

1) On an old wooden yacht, bouncing around in the Adriatic, caused the battery to come adrift & shorted due to a metal strengthener beam. Lots of smoke, but soon sorted.

2) Just off Cowes entrance, when the starter solenoid continued powering, due to key starter not springing back start position. Again lots of smoke & some panic from punters. Dealt with, by turning all power off.

Never had a problem with diesel - difficult to burn even with a gas flame, as demonstrated on firefighting courses.

Hot debris, oily rags etc, can be a cause, which is why engineroom cleanliness is important.

Only other experience, was in the caribbean, when a nearby charter yacht caught fire - believed to be gas problem - burnt to waterline in about 10 mins.
Gas, has been the cause of many injuries/accidents.

 

[prv]

I was going to suggest electrics as the most likely cause - reading through the thread that seems to be borne out by others' experiences. The difference between the engine bay and anywhere else is that wires elsewhere are (should be) protected by fuses, whereas it's common practice not to fuse starter and alternator cables. In addition those wires are bigger, can supply more current to the fault, so instead of a hot spot and a little smouldering you get big sparks and lots of heat - essentially it's a welding set kicking off inside your boat.

For this reason I do have (large) fuses in both my starter-motor and alternator cables. Of course the one on the starter has to be pretty large, so there's fair potential for nastiness without it blowing, but hopefully if the cable were to short onto the engine block or similar it would draw enough to blow.

I also have an auto extinguisher in the compartment.

Pete