AM/FM/CD Radio Fire in a Boat

Lightning bro!

I'll vote with Jack on this one.

You may consider (If you know your way around these things) getting hold of a can of electrical polyurathane to coat the circuit boards in the radio. Just keep it clear of moving parts like cd scanners and tuning buttons/dials. That's the key difference between car and marine. Also lube all moving bits with an electrical lube (anti corrosive and non-conductive). You will have to do the lube thing every couple of months or your controls will corrode up, the marine ones come with corrosion resistant parts, car ones don't.

Have fun, stay afloat and be cool!(no Fires)

i question the lightening strike theory............i was on board during a storm when lightening hit my marine band antenna on the top of a 54 foot wooden mast.

the flash was blinding, the sound was deafening, and the antenna was vaporized....the current ran down the safety grounding strap into the water.......

imho, if that much energy came down your antenna wire, there would be alot more damage to your radio than what you experienced....

also, you didn't notice the second damage , untill a few days after the first,,,,i think you would have seen everything the first time if the second damage had already existed....

do you have leaks around that area ? could water have come down the antenna wire and short it to power????

hmm, i'd like to debate this further, with feedback from the OP

..............wouldn't the lightning strike result in a catastrophic failure, wouldn't the radio have been fried, as it would have been the direct link between the electrical energy surge and ground.......?

what would have made the electrical surge stop where the antenna enters the radio.....where did it go? into the fiberglass ???..... i'm betting that the way the radio is mounted that there is no direct electrical path between the radio chasis and ground...... wouldn't have destroyed the antenna lead, not merely melt it ????

if it did exit there, wouldn't it have been like a mini explosion...........

and if there were open flames what put the fire out ???

the description of the damage sounds more like the wire was slowly heated up until it got hot enough to melt..................

there is more than enough juice between a hot wire on the boat and ground to melt a wire.............it happens in cars all the time.............there is alot of potential in a 12 volt battery.........

At least SOME car radios put a DC voltage onto the antenna lead wires, in order to power the amplifier built into the antenna base; a capacitor couples the signal but not the DC compnent. It should be easy to determine whether the radio you've chosen does this - just hook a meter to the input jack with radio hooked up to power. MOST will be off if the radio is off, but I don't know if that's universal. I think most aftermarket car radios today are capable of providing power to the amp (note how many cars you see with tiny little antennas, usually just above the rear window opening).

FWIW, I learned about these when I bought a car second-hand, and the AM radio worked (poorly, with losts of static, like ALL stations were at fringe reception signal strength) but not FM. On that car, the amplifier ground was through the antenna mount, and cleaning the underside of the roof and re-installing the star washer and nut cured the problem. The shop manual (Bentley Manual for VW) actually had a troubleshooting section on the radio!

Sounds like you do need to fit a correctly rated fuse. It can be one that supplies both positive connections.

Are there also not safety devices available that direct possible lightning strikes straight into the water? I guess the radio might still be screwed, but no flames (assuming it was a lightening strike...)

Just a thought!

My mast is grounded to the keel bolts and also to a large copper plate which is on the bottom of the hull with large gauge wire, at least #6. The fact that I first noted the melted insulation then at a later date found that more wires had also melted insulation leads me to believe that if it was lightening, the strike only did part of the damage, and perhaps caused a fault which later caused the rest? One argument against lightening, at least at the antenna itself is that the 50 feet of coax from the mast top antenna to the radio is still ok. No physical signs of damage are on any part of the coax that I can see and once I put a new connector on it, it works with the new radio. If enough current to melt the rubber off of what looks like #14 or 16 wire attached to the radio had traveled down the coax, the coax should have been vaporized but it seems fine. Lightening could have hit the radio directly through the upper part of the boat but I'd expect to see external fiberglass damage in that case and don't see any.

Thanks for all the discussion. It has been interesting. I'm going to check to see what the fuse on the new radio protects and if it doesn't protect both hot wires, solder an in-line fuse in battery lead.

May be the mast is open circuit to ground, thereby the mast may be discharging lightening strike through radio ground. You may consider putting a lightening arrestor in the antenna line to prevent recurrence of this kind of blowups.

A primary strike on an adjacently moored boat with a partial bounce to your boat (Highly Speculative) may explain the "softer" damage experienced compared to what might be expected from a direct mast strike.

Some interesting comments on this very scary subject. I've seen what was left of a boat that took a direct hit......only what was below the waterline remained. Total write off. Also lucky no-one was on board at the time.

hi can you describe the fitting of the mast?

45 foot aluminum secured at the base?

also where is your VHF airiel mounted?

you might like to fit a low value capacitor in the airiel down lead on both inner and outer of coax to break any DC path

there may be somthing connecting to the mast that your not aware of.

try checking with a volt meter connected to mast and neg side of battery and then pos side of battery.

and post a reply giving your findings

OK, I'll do that but I only get to the boat every few weeks in this lousy weather so it might take a while.

All I can think of is that the first power lead may not be fused (it certainly isn't on a breaker),

You need to install a fuse in the constant power wire as if you did get an internal short then you could definitely see melted wires and an acrid smell from the burnt insulation. Good Luck

I witnessed "St Elmos fire" through a pair of binoculars during a lightning storm decades ago. it lasted several minutes. too far away and too many other lightning hits to determine if there was any thunder or sound generated. ground struck /originated by lightning was a few kilometres away. you may have actually been "conducting" a large amount of energy for more than a few moments and enough energy had dissipated to prevent a "lightning strike". ? there has been lightning hits without the usual thunder. European soccer game killed most players years ago without the visual lightning or audible thunder.