Running engine... electrical isolator switch knocked OFF ! Desperate for help...

[Marcus_J]

I was motoring along at reasonable revs yesterday when I lost trim and then found all my electrics were down. Found too that the electrical isolator key had managed to be in the OFF position while motoring. Oh dear. The battery was steaming and all was dead and remained so. I cut the engine and then of course could not restart it. Battery hot - safest to remove + and - and let it cool. Dropped anchor and was picked up. My crew, the missus, 7 months pregnant, seemed content enough.

I am assuming the alternator will be cooked as well as the battery. I could find no blown fuses. My major concern is that all wiring may be ruined, though as I say, there's no visible damage. I would be really grateful for any advice on where to start. I am based near Falmouth so there is no shortage of pricey sparkies upon whom I could call, but am keen to do as much myself as possible.

Thanks very much indeed.

[jwalker]

If the battery was hot then it's likely to have had either a major discharge or a major over charge. There must still be a battery connection even though your main switch is off. My guess is an overcharge where there is still an alternator to battery feed but no regulation because the engine ignition supply has been disconnected.
We need more information. What engine? Have you checked the battery and its electrolyte level? Have you reconnected and tried to start the engine? Are your electronics working or damaged? etc. You may find everything is ok.

[Polwart]

I'm no expert so I'll leave suggesting how best to start unpicking the damage to someone who is; but here are my immediate thoughts:

(1) the wiring should be fine as that is why it has a fuse to protect it - if the fuses haven't popped then the wiring shouldn't be damaged [note that the main battery to engine cables are unfused - but are beefy enough to withstand most things].
(2) if the isolator was OFF the battery shouldn't have been getting any power from the engine - so why was it "boiling".
(3) it sounds as though the "regulator" (which controls voltage from the alternator) may be faulty - that would boil batteries; the alternator itself may be OK?

Glad you got home OK in the end; You might want to find out how to start your engine without a battery (most engines can be pull started using a rope if you know how) - as then you can limp home pretending you are "in control"!

[Erin]

Welcome to Ribnet.

I can't see why the battery got cooked. If the isolator switch was 'off' then it should have been safeguarded from any damage, unless current found a way through via some other route. I have heard of a case where a bilge pump has leaked current back to a battery, the wrong way as such pumps usually bypass any isolators so that they are 'always on'.

There's a good chance your alternator/regulator is damaged, but the first thing I would do, is try a fresh battery and see what happens. You may have been lucky. If your GPS or a multimeter shows batt voltage at over 12v with the engine running then that would suggest the alternator is ok.

Check all cables visually for any overheating etc. If properly wired, fuses should have blown to protect the electronics. It all depends on how it is all wired up. I'd possibly change the isolater key to a more positive switch. Hella/BEP make a good high current one.

[Marcus_J]

Thanks very much indeed to everybody for their thoughts. First time I have used the forum so very grateful.

If I can try and answer the questions asked:

The engine is a Yamaha 115HP autolube. Too big to hand pull I think.

I tried a different, fully charged battery which I have at home and still nothing - engine will not turn, not even nav lights. Totally dead.

Once repaired I will certainly change the isolator switch to one which fixes ON/OFF better.

No sign of overheating after visual check on all cables.

I agree, sounds odd, but I am sure I have read that running with isolator OFF causes too much charge to the battery but I still can not see why the new battery did not solve things.

Where might I find the regulator ?

Thanks again to everybody for their advice. Please keep it coming, I am very keen to crack this.

[Polwart]

Originally Posted by Marcus_J

The engine is a Yamaha 115HP autolube. Too big to hand pull I think.

you might be surprised! You can find your manual here: http://www.yamaha-motor.com/outboard...px?ls=outboard

I tried a different, fully charged battery which I have at home and still nothing - engine will not turn, not even nav lights. Totally dead.

It might be useful to understand the wiring on your boat. Normally the Nav lights will work even if the engine is not fitted! Could be your isolator switch is shagged? Either that or you've got some fuses you don't know about! (e.g. are you aware there is a master fuse somewhere under the engine cowl?)

[Erin]

If nothing's working, then there must be a fault with the isolator switch or the main cables running out or back into the battery. I think the regulator is normally bolted on the top of the alternator, sometimes sits under a plastic cover, although on some outboards, it is mounted on the side of a water jacket on the engine to get some cooling.

[slimtim]

Polwart, I would be interested if you know of a technique that enables you to pull start an engine of this size. I tried and failed to pull start my 70hp tohatsu and that's obviously far lighter than this yamaha. The compression resistance and stroke of the pistons is too great!

Have you had better luck?

[Polwart]

Originally Posted by slimtim

Polwart, I would be interested if you know of a technique that enables you to pull start an engine of this size. I tried and failed to pull start my 70hp tohatsu and that's obviously far lighter than this yamaha. The compression resistance and stroke of the pistons is too great!

Have you had better luck?

Tim, I've only had to do use an "emergency start rope" once, I think that was a 90HP 2 stroke but it might have been a 70HP as it was a while ago. No that difficult as I recall.

[jwalker]

And I've done it on a 200 Suzi without a problem, it even came with a cord and handle. Slightly scary the first time, fortunately it was the only time.

Start with a meter at the battery and work along the power cable until you find the disconnection. You need to suss whether all/some of your accessories are powered via the engine ignition or directly from a battery circuit. The problem will likely be in a different place depending on which. Distance engineering is difficult without all the information!