Ignition wireing Potential hazard found

[markcw]

Seeing the pictures of the burnt out boat, nudged me to sort out a on going electrical issue with my boat and in particular the loss of 3volts when ignition is turned on, V/P manual states a drop of 0.5 v max so were it going, done a bit of research on the American web site and my attention was drawn to a high resistance cable fault which other boaters have also found

With circuit diagram out fluke meter on disconnected all ignition leads form dash to engine Ive worked through resistance checking all cable harness, well surprise surprise when metering the high current leads between starter- rcd- and alternator a resistance of 978 ohms was found on a red cable, cleaning and checking ends no improvement was made still a very high resistance.

so for the last hour i taken out the whole engine loom to do a proper check and to my horror there is no continuity between one of the two spliced high voltage cable that runs to the starter and back to auto fuse so the other working cable could of been recieving double the current that it should have, also found very poor and corroding ends.


The loom was checked two years ago when i removed the engine, so goes to show how quick things start to wear.

So i am going to replace that part of the loom for new and hopefully all other cables buzz out with no resistance.

An hour of checking the loom could stop a major melt down.

Be Warned

markw

 

[elton]

I'm not clear exactly what you're measuring or how you're doing it, but cables don't just develop a 'resistance'. Badly made connections may exhibit resistance, but will be effectively open circuit when under load, resulting in the load device remaining unpowered (off). Also, bear in mind that the ignition coil is likely to have a ballast resistor in series with it somewhere, which is short circuited by the starter motor solenoid.

 

[rbcoomer]

I removed 4' (12cm) from the battery end of the power leads to my outboard for the same reason - corroded and powdery inside, high resistance and poor starting performance. Moisture tracks inside cables and if that moisture is salty then it will ultimately corrode. If you can't get back to clean copper (or tinned copper) then replace the cables. Resistance=heat under load and not good in something made of plastic and filled with fuel! A marine grease or sealant around the ends (not on contact surfaces) will prevent most water ingress.

 

[markcw]

My system does not have a ballast resistor as the coil and spark module was upgraded with pertronix 12v system inc electronic spark module, before fitting the system the ballast resistor must be removed, the resistor is used on 8v coil and points in the distributor.

I agree a high resistance can and will be caused by a poor or corroded terminal, but that does not stop the fact that the spliced wire will then have to take on the extra current due to one path being faulty,

A cable that take over its max current load will give a high resistance and heat up or burn out depending on its gauge and max load.

My point to the tread is the checks we should all make to the wired components in our boats, my issue started with a 3v drop when ignition was on no 1 (not cranking) the only demand at that position is gauges, and relays to circuit. volvo penta manual states a 0.5v drop max at position 1 not 3v, all gauges, fuel-pump-temp-oil pressure sender should have 12 upon cranking they have been receiving only 10v

 

[Assassin]

When any water enters the cable, and it is a place where the cable constantly moves, it just begins to snap the cores one by one until they have snapped through. As they snap the resistance increases, once they all snap only the ends rub together to form any sort of contact.

Its a common problem on pure off road vehicles as well.