Tracing a fault

Pedrode · 03 July 2013, 22:11

Looking for some advice on how to trace an electrical fault. Went for a 40 min potter about today, went ashore for 20 mins, returned to the boat, engine turned over once, then nothing, no tilt either....but the anchor light still worked. The anchor light went out when I tried the ignition (with no success) but then came back on again. Returned to port using the aux and had power again briefly - enough to tilt the engine back up but not enough to turn over the engine. My prognosis is that the battery is not charging either as a result of a bad connection somewhere or just a duff battery. Charging the battery overnight and will see how it behaves tomorrow. Guessing I need a multimeter or something like that to assess whether there is a charge coming from the engine or not?

The only other thing that I thought about was that I left the isolator switch on while we were away for 20 mins, but don't see why that would drain the battery.

The engine is a 60hp Mariner Bigfoot 2004 vintage.

Electrics not my strong point so any advice much appreciated.

Erin · 03 July 2013, 22:13

Sounds most likely to be a bad connection somewhere. Check the connections to the battery and also at the outboard end. I would suspect a loose or corroded terminal.

freespirit3 · 03 July 2013, 22:22

Have done this myself before, you can drive yourself mad testing and checking.

Your on the right page charge the battery and recheck battery tomorrow

The light going off is a result of the engine drawing all the current, the battery should be capable of starting the engine with the nav lights on, they might dim very slightly but no go off.

If it is the battery, try and get a good marine leisure deep cycle battery as a replacement, worth it's weight in gold.

My last one on my humber lasted 8 years. See if you can get hold of a hi discharge battery tester, this simulates a cold engine start and normally has a volt meter to show the volts

Best of luck

Nos4r2 · 03 July 2013, 22:25

It's probably not the battery if it started ok for the 40 minute potter. It'll probably be dodgy battery connections or a dying battery isolator switch.

freespirit3 · 03 July 2013, 22:26

Forgive me, I am taking it for granted that all the connections to the terminals are in a good condition and tight.

Best of luck

Pedrode · 03 July 2013, 22:55

Quote:

Originally Posted by freespirit3

Forgive me, I am taking it for granted that all the connections to the terminals are in a good condition and tight.

Best of luck

Thanks. That was the first thing I checked. Earlier this year, I had to trim back the positive wire because the exposed end at the terminal had become brittle and started to break. I trimmed back to good wire and that solved the issue. The neutral wire seemed fine today but I might just trim it back in case there is a break just inside the insulation. I really enjoy my RIB but it does seem to be one thing after another these days - the joys of a 12 year old boat and 9 year old engine!

Pedrode · 03 July 2013, 23:02

Quote:

Originally Posted by Nos4r2

It's probably not the battery if it started ok for the 40 minute potter. It'll probably be dodgy battery connections or a dying battery isolator switch.

Yes, the battery has been fine to date - and it does seem to be taking a longer time than usual to reach full charge this evening which suggests it was very low in power to start with. I guess a dodgy connection would have two effects - no charge in and no power out. On the bright side, the aux needed a good run, uses a fraction of the fuel and just for once the wife wasn't shouting at me to slow down on the way back!

rossymtb · 03 July 2013, 23:04

Im not experienced with a rib and all the electrics but... My car once did a very similar thing lights would not work/ would not start/ Battery was fine and connectors where tight but the actual positive and negative battery terminals were dirty. Cleaned them all and i now do that on every other car i own along with all the earth points, Might give you somewhere to start just a thought.

ppenman · 04 July 2013, 08:54

I had a similar problem a couple of years ago. It turned out to be the isolator switch. One new switch and all was fine.

Pedrode · 04 July 2013, 21:51

Lots of helpful suggestions which are much appreciated so feel obliged to provide an update which, in summary would be: Bugger, its a loose connection. I see before me endless hours of checking connections and wires. It would have been sooooo much easier if it had been a duff battery. From now on, please treat this as a blog / soap opera with a series of hopeful updates followed by crushing disappointment as I eliminate the possibilities one by one. So....checked the battery. Showing 12.8 volts after the charge last night so that's not the problem. Cleaned all the terminals and checked the engine end. Power seemed fine - engine tilt etc. Back in the water, one turn then dead again. Put my hand into the battery compartment, shoogled the battery wires one after the other and, after moving the negative/neutral wire, hey presto started first turn. Went for a run staying near port, tried a few stop / starts and no issues. Problem is, I don't know whether its a break under the insulation in the neutral wire or I moved another connection. Its a real tangle of wires in there but, I guess that the only wires that run to the engine are the two from the battery (via the isolator and ignition) - or are there other critical ones?

spartacus · 04 July 2013, 22:14

Could be corroded or break in the main power line. It's not particularly expensive to change, so that would be my first port of call. Fit tinned cable if changing.

martini · 04 July 2013, 22:34

If I were you I'd just replace the heavy gauge battery cables and be done with it. Sounds like the current ones are corroded bare copper with dodgy crimps on the connections. New tinned wire (silver in colour rather than copper) with professionally crimped or soldered lugs would mean you wont have to worry about them again for many, many years.

jambo · 04 July 2013, 22:39

Had simar problem a few years ago bad starting. The cables were badly corroded so replaced them. Sorted

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Nos4r2 · 04 July 2013, 22:53

Should be fairly easy to find, and I'd almost bet it's the main negative terminal itself, or the cable into it.

Erin · 05 July 2013, 13:19

One possible scenario is an intermittent fault inside the battery. One of my cars had this recently. The battery was a decent Varta, less than 2 years old and would start the car fine one minute but not the next. Obviously each time I went to the factor it would behave itself, but they eventually took it in overnight and tested it and agreed it was faulty. Got it replaced under their 3 year warranty. So, if absolutely everything else checks out ok on your boat then maybe swap batteries with your car if poss and see if the fault transfers.