Engine fire

[SEMPERAVANTI41]

I cannot be sure, but everyone, please take a look at the attached pictures of the fire aboard my old Hunter 50. I was always suspect that the alternator was at fault. The fire occurred almost 2 years ago, and no one (including Progressive Insurance) could figure out what caused the fire. BTW, the boat was at anchor with the engine off when I noticed smoke rising from the engine compartment. I have not mentioned the brand of the alternator on purpose.

 

[dlochner]

The alternator is from a well known brand and likely a retrofit from the OEM alternator, as the J10 pulleys are not stock.

It is impossible to tell from 4 photos what the cause of the fire was, however, electrical fires are among the most common on a boat. These are caused by inadequate or absent over current protection, poor installation, chafe, and ultimately a short circuit on the positive cable. If I had to venture a guess the wire from the alternator output chafed against the engine block, shorted and started the fire. The use of undersized split loom on the cables suggests a shoddy installation.

Did the insurance company hire a qualified investigator? The origin of an electrical fire should not be that hard to trace. There may have been other factors contributing, such as a fuel leak.

 

[marcham]

Is the red wire going to the alternator fused near the alternator? Was the start battery switch ON? Is the alternator output wired directly to the batteries or does it go through the Start battery switch?

I would determine if it's possible that the positive alternator post contacted the engine....

Engine was a 4JH? ?

 

[Don S/V ILLusion]

take my word - no one here can lend an educated guess. Having been through this, watched a state Fire Marshall as well as the local fire department and an insurance investigator crawl around the remnants, none of whom could ascertain this cause, a blind squirrel will have better luck than anyone here.

 

[kloudie1]

Third picture from the left; That green copper really suggests a chafe that let seawater in under the insulation and made for really bad connections.. lots of heat there.. usually, when a cable fails because of conducting too much current, the individual wire tips at the break will have kinda spherical ends.. again usually, when a wire fails in a fire because of the fire, the ends of the individual wires will be tapered and kinda pointed.. That's all I see.

 

[Ralph Johnstone]

take my word - no one here can lend an educated guess.

And that pretty much sums up the entire situation. Crawling through the engine, in person, is an absolute necessity to even begin to form a theory on what started the fire.

The only safeguard here, short of an an internal fire suppression system, is to know your engine well and get in there at the start of every boating season and look, go through, investigate, observe, scan and probe to see if there are any burned or chafed wires. Raw water leaks and diesel leaks are also a source of present or future problems.

 

[jssailem]

Wow. As stated, would need to be in front of the engine to even develop a SWAG.

 

[BAD ORCA]

Third picture from the left; That green copper really suggests a chafe that let seawater in under the insulation and made for really bad connections.. lots of heat there.. usually, when a cable fails because of conducting too much current, the individual wire tips at the break will have kinda spherical ends.. again usually, when a wire fails in a fire because of the fire, the ends of the individual wires will be tapered and kinda pointed.. That's all I see.

Its hard to say anything is in its original location, but that same wire in the second picture looks like it makes a giant loop in front of that belt pulley, and is very close to those spinning bolts directly in front of that green area of the wire. Did it rub against the bolts and eventually relax back and touch them with bare wire? The discoloration of that pulley almost looks like a soft flame lapped up and around the pulley.

I wonder, could it have shorted to one of the bolts, started the wire insulation on fire and then causes a fault in our near the alternator which really began the major part of the fire? That alternator and wood next to it looks extra crispy.

It begs the question if that particular wire is fused?

 

[SEMPERAVANTI41]

The heavy red wire was cut by firemen, who also sprayed the entire boat with salt water. They even opened up the FP generator and sprayed it.
As far as wiring, the only change made to the original Hunter wiring was an alternator harness from the aftermarket alternator manufacturer.