Isolator switch - how essential are they?

[ivan4199]

My isolator switch next to the battery has just failed. I may not be able to replace it for a few weeks so the boat is sitting in the Marina without the battery shut off. Bit worried about leaving it & wondered how urgent it is to get this sorted. There's a slight risk kids could muck about raising and lowering the engine, playing with lights etc. but I'm told kids hardly ever trespass onto the marina.

Apart from this slight risk are there any other problems with leaving the boat without the isolator shut off? Thanks in advance, Ivan

[Lewy]

if you have an automatic bilge pump and no cover on the boat, and it rains alot, that could drain the battery.
hopefully it'll be nice and sunny for a few weeks.

[Poly]

Originally Posted by Lewy

if you have an automatic bilge pump and no cover on the boat, and it rains alot, that could drain the battery.
hopefully it'll be nice and sunny for a few weeks.

but if you don't the boat might sink!

[PeterM]

One of mine has switches the other doesn't - but the one that doesn't sits in the garage so not much chance of it being played with by kids ( apart form mine) .

Not sure if there is a 'real' safety issue in terms of fires etc - all out cars dont isolate the battereis they dont ( often) catch fire.

Mine with the isolater swithces still runs the bilge pump & then doesn't start when its rained a lot ! I thin kis mainly down to needed a new starting battery rather than anything.

I'd guess you would be fien for a few week , but I'd be reading the insurance policy just in case & double check the lights etc are turned off !

[tinker]

IMO they are important for safety when at sea. I have 'played' around with car batteries as a youth and when they short out the heat generated in the cables melted the PVC insulation in seconds and the 2.5mm2 copper conductor glowed orange within about 5-10 seconds. The risk of fire is quite high and a bonfire on a boat with all the fuel is not particularly a good idea.
PS Its a job I need to do as well.

[ollyit]

I think there important, but just as much also peace of mind of example when you're on a trip and you have to moor and go to on to land for whatever reason, isolating the power at the source via the switch or pulling off the battery clamps ensures nothing will be draining your battery, theres no worse feeling coming back to battery later on to have a couple of very sluggish cranks of the starter and not enough to fire your outboard for your trip home - I've had one actually break on me to, it broke internally and make partial contact very intermitterently causing the fishfinder to power off and on continuously - very annoying - cheap enough to replace though, and you cant have enough spare red keys!

[Andy JC]

To remove the battery clamp it's usually only a single nut, can you not just temporarily pull one of the clamps off?

[waverunner]

From personal experiences I would certainly fit one.

When I put my rib package together I was advised (by a dealer) not to fit an isolator because apparently ECU,s don't like them, just connect from the battery direct to the engine starter solenoid.

I had a good day out, recovered the rib onto the trailer, sat with the family having a sandwich and brew, suddenly the engine started to turn over and I had no means of isolating. It was a mad rush to find a spanner to disconnect the battery, by the time I had done this the starter motor had burnt out. I had to have a new starter motor and pump impeller fitted due to it being out of the water and running dry.

The culprit was found to be a loose connection on the starter solenoid.

[ollyit]

jeez, I think you best off buying one for the sake of £12 or whatever it is after reading story above, imagine if that had happened when changing over a prop, u'd brick it at the very least, think of it as an additional security device too against boat theft,

[m chappelow]

once got called out to a yacht that had been sinking when we arrived the water level had started shorting things out sizzles and sparks everywhere but we couldent reach the battery leads if the boat had been fitted with an isolator it would have made things easier in the end the battery exploded having about the same force as someone hitting the hull with a large sledge hammer .

[alystra]

Didn't have one for five years, so they're not essential. Then realised if there was a short for what ever reason something might start to work - trim/tilt, starter, anything. Thought of the expense of the tilt motor trying to pump against the stop, or starter burning out or a fire, and fitted one. Peace of mind now.

[Nos4r2]

Agree with olly and M Chappelow.

I've had one go dud on me while out as well-had to bolt the two terminals together while at sea because I didn't find out til I tried to start the engine in Poole Bay and it wasn't a nice job as salt water is a very good electrolyte.The jolts up the arm are quite disconcerting.

It's worth being able to disconnect the electronics separately (easily accessible main fuse or switch) because the first thing that will happen unless your electronics are hardwired to the battery is the input voltage will rise dramatically and maybe start frying stuff (mine fried a VHF in that incident). If you see the system voltage shoot up then it's worth turning everything off immediately.

Your engine should carry on running with the switch off-just don't stop til you get to somewhere safe to bolt the two terminals together...

[Andy JC]

Another alternative is to use these

Very effective, been using them on the caravan for years without any problems. Also means changing or removing the battery for whatever reason is a 2 minute job

Just ordered another set for the boat

[9D280]

Yep, I had a battery switch on the old boat that went swimming, after I got swamped. < 4 hrs later it was as good as useless. Thankfully the engine had a recoil as well, so I could at least stop it & know it would restart.

I ended up with putting 2 wing nuts on the terminal posts of the new switch, and crimped together a short loop wire with 2 suitable sized eyes which lives in the toolbox.

On my current boat the switch is above the "flood line", as are the battery terminals, so hopefully I'll never need to use it.

[J S]

Originally Posted by Nos4r2

Agree with olly and M Chappelow.


Your engine should carry on running with the switch off-just don't stop til you get to somewhere safe to bolt the two terminals together...

You just have to be careful on the more modern engines with an ecu as it can damage it, the engine will carry on running but will show up fault codes etc, and may need replacing.

James

[jyasaki]

Originally Posted by m chappelow

once got called out to a yacht that had been sinking when we arrived the water level had started shorting things out sizzles and sparks everywhere but we couldent reach the battery leads if the boat had been fitted with an isolator it would have made things easier in the end the battery exploded having about the same force as someone hitting the hull with a large sledge hammer .

Cut the battery cable, assuming you could reach it.

Had a similar scenario with a car; short somewhere, battery cables smoking and insulation melting. Chopped the cable (faster than loosening the nut and disconnecting it) and everything stopped.


jky

[ribpilot]

Panic Panic Panic.I've got marine terminals with quick release wing nuts but no isolator switch so after reading about wiring shorting out and things catching alight I'm going to disconnect my battery now.Sounds like a good idea to have one fitted.

[BruceB]

They are not essential in that the boat will work without one, however everybody is assuming they will be around if it all goes haywire and things start shorting out.
Boat wiring is in a poor enviroment and is not always of the standard that it should be. I have always had one fitted on every boat for emergency shutdown when I am on it and something happens (never yet thankfully) but more importantly shutting down the system when I am away so it isn't possible for the boat to turn itself into a molten puddle due to a short or problem.
I have had a car, twenty ears ago and a heap admittedly, start smoking from under the dash due to a short. Luckily it was just as I pulled up at home and I managed to get the battery off before much more than a few melted wires were caused under the dash. I dread to think what would have happened if it had been 5mins later once I had got out and went inside.........
its a peace of mind thing really.

[Leapy]

Originally Posted by J S

You just have to be careful on the more modern engines with an ecu as it can damage it, the engine will carry on running but will show up fault codes etc, and may need replacing.

James

Is this true? In what way does the switch cause the ecu trouble that is avoided if you disconnect the power cable from the battery?

[Chris]

Originally Posted by Nos4r2

Your engine should carry on running with the switch off-just don't stop til you get to somewhere safe to bolt the two terminals together...

Won't that fry the alternator?