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I guess that I'm a typical sailor, just as inclined as anyone else to bury my head in the sand and think "it'll never happen to me". Well, it didnt't happen to me, but I saw the consequences of someone else's boat fire - one that could possibly have been prevented.

The fire occurred in a well maintained Sadler Starlight 35 when engine movement in storm conditions wore through the insulation on the starter motor cable causing a dead short. The cable went to red heat, the insulation caught fire along with some of the boats fittings. The red hot cable melted through the tops of two of the three batteries allowing some acid to escape. Luckily, and perhaps surprisingly, the main isolation switch still functioned and the crew were able to stop the fire at source and put out the secondaries. It still left them in a fume filled engineless boat struggling with quite bad conditions.

They made it and didnt end up a statistic. But the whole problem could possibly have been avoided if there had been fast acting 100 amp fuses in the main power lead. Simple, and not that expensive.

Trouble with this sort of story is that for every person who reads and acts on it, far more will simply move on. All I can say, is that having seen the state of the casualty boat personally, I will not simply move on.

Incidentally, I intend no criticism of the crew involved. They coped magnificently, and in any case "there but for the grace of god...."
 
Why, for the sake of a few quid...

Why, for the sake of a few quid, don't boatbuilders automatically fit fuses to the starter and domestic battery banks? Shouldn't the boatbuilders' federation (whatever it's called) demand this as a basic safety measure? Of all the things on a boat which offer a real danger, the battery installation must count as the number one suspect.
 
Boat price / investment ?

Lets be honest ...... I don't think there is anyone out there without an economy somewhere on his boat .... EVEN in the safety arena.
Its ok saying Boatbuilders should fit these ...... but generally the final question and decision lies with the owner / purchaser ...... who always demand less price, more kit .... when the builder / supplier quotes additional - the cheque book suddenly goes quiet !!!!

When it comes to s/hand boats its even more lax ...... we buy a boat and plan what additions / amendments we are going to do ..... more than half never get done, the other are nearly always done at minimum ! There are also a lot out there that fall into the ..... its been alright for years, why should it fail now ??

So what is the answer ??? I agree that safety is 'Numero Uno', also that practicality has a great deal to do with it.


Nigel ...
Bilge Keelers get up further ! I only came - cos they said there was FREE Guinness !
 
These heavy amperage fuses are relatively new technology so you won't find them on the average boat. I first came across them some years ago in an article by Nigel Calder but couldn't source them except for crashed Mercs and BMW's. Since then you can get them from Radiospares. I've fitted the 300 A onto my battery bank. They cost roughly £4 for the fuse, £2 for the stud and £4-ish for the pole connector if you need it. The fuses range from 50 to 300 Amps and fit directly
onto the battery pole which must be the best position for this type of fuse.
There is another type, glass-encapsulated, that is mounted remote from the
battery. Fitting is easy but may require changing the terminal on the cable: the
RS type requires a spade with an 8mm hole. Fitting this onto a 25 mm2 cable
requires a special press (friendly garage or electrician). Then run the cable in a
PVC sheath (on its own). And tie it where you can.
 
I don't know what your link looks like, but I have not seen this type of
fuse installed on a car. I'll try to describe it from memory (and then go to look
at it on the boat...): the body is circular, about 20mm diameter and about 20 mm high with a hole in the middle to slip over the 8mm stud set into the pole
connector on the battery terminal. The fuse strip runs up the side: the bottom
bit is in contact with the pole connector, the top connects to the cable via
an insulated screw.
RS have a web site: I'll look it up together with a parts ref and come back.
 
Circuit breakers will be more reliable, and if you check radio spares or maplinselectronics on the web you find prices for all size ratings. I have/had 80amp one for various items but when I needed it most the one circuit that blew everything wasn't protected and the main isolator switch melted the current was so heavy after the battery bank was submerged for a couple of hours. Six batteries best part of £300, one circuit breaker under a £10.

Phil
 
Excellent but what fuse size??

These look good. I think I've found them on rswww.com as 337-7937(100A fuse), 342-0205 (Holder) and 342-0198 (insulated nut). My problem is that that the wire connections to my battery are not crimped onto tags but screwed into the battery terminal connector itself so I need to find someone to crimp some tags on (perhaps a Car Audio installer?).

My 29ft sailing boat has a 20hp inboard diesel - could someone advise me - is 100A a good fuse to fit for this installation?

Thanks

Gavin
 
Check out the MEGA fuses...

About the best high-amperage fuses are branded "MEGA" and fit into a very well-engineered holder which has big studs to bolt the cables to and rubber boots to cover the terminals. They are available in 50 to 250amp ratings. You can see them on the - they're called "Sea Fuse". They're available from good chandlers or from <A target="_blank" HREF=http://www.indexmarine.co.uk>Index Marine.

The purpose of the fuse is to protect the cable, so that it won't overheat. The fuse rating therefore should be around the same as the max current which the cable can take. For a starter circuit, I'd normally use a 150amp fuse.
 
I had a starter short once, could have been very nasty, however I soldered rather than crimped the connectors to the cables. When the short occured, things got very hot and exciting till the solder let go and the circuit broke. Still I dumped the entire contents of a CO2 extinguisher into the engine room just in case.

I have been looking for a fuse to the starter ever since, but not had any luck and most of the books that you read about boat electric don't talk about them either.

I'll try index and see what they have.

regards,

Nick

Despite the high cost of living, it still remains popular.
 
I've just been looking into this and have sourced the Mega fuse and holders from ASAP supplies. I have also had 2 0.5 metre cables made up with tags with 8mm holes at my local auto electrical shop. They cost 12 quid for the pair. As I wasnt sure what cables the boat had from batteries to switch I went for the biggest they had which is very thick but better that than too thin I would imagine. It does seem quite flexible though.

While I'm doing this I've decided to protect the power cable to the main fusebox with what ASAP call a Midi fuse (like the Mega but smaller with much smaller attachment posts) as I guess that the 150 amp fuse would be too high to protect that circuit correctly. I suppose the directly connected bilge pump should have a small one too.

Gavin
 
What size fuse?

I'm resurrrecting this thread as I would like advice on the correct size fuse for the starter current on a Volvo 2010 diesel. Should I go by the thickness of the cable between the starter motor and the battery?
 
Re: What size fuse?

In normal electrics yes you'd purely size based on the size of the cable, however this may be marginal with an engine that's stone cold, thick oil etc. At this point stall current on mst starters is around 250-300Amps only short term admittedly.
Assuming it's a Diesel then I'd fuse around the 250A mark. This would protect from fire in the event of a dead short but should cover the various starting issues, I'd not expect this to be much, if any above the cable rating.

Jim
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If you\'re using a MEGA fuse...

If you're using a MEGA fuse, you could specify a lower rating - say 150A or 200A - because the MEGA fuse is relatively slow to blow. At 135% of rated current, it takes at least 2 minutes to blow, giving you a useful margin.

The starter circuit on my Volvo 2003 is protected by a 150A MEGA fuse.
 
Re: If you\'re using a MEGA fuse...

I've got the Index Marine Equipment catalogue. There is a High Amperage fuseholder and fuses from 100 to 300 amps. They look similar to the MEGA fuses. So would a 150A fuse from them be OK?
 
Re: If you\'re using a MEGA fuse...

Yes if they're that slow blow then you'd be OK.

Jim
------
 
Yes...

The Index Marine fuses are MEGA fuses, made by Littelfuse. Good info on the <A target="_blank" HREF=http://www.littelfuse.com/PDFs/Products/298.pdf>Littelfuse website</A>.
 
Being not very electrically inclined myself, I see this in a somewhat different way from most other contributors to this thread. Every boat DIY book or article that you can find will offer some sort of advice about clipping and supporting cables to guard against chafe and short-circuiting. Millions and millions of cars have batteries, starter cables and plenty of engine movement, but they don't have high-current fuses and they mostly don't catch fire. If the cable had been installed correctly (either by the manufacturer or possibly after modification by an owner) at very low cost, then the problem would not have occurred.
 
In this particular boat the cable ran between the engine sump flange and the engine bearers. Dont know whether this was standard or the result of a mod. It was when the engine moved on its flex mountings in foul weather that the prob occurred.
Most boats dont catch fire, so you are correct in that sense. However, there are possible causes of a dead short however well the cables are tied down, and the cost of protection is so small. So why not be safe anyway?
 
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