Battery cable problem?

[stevecray]

I have a 2004 Ribcraft 585 with a simlar age Honda BF90 that started fine 2 months ago but now seems unable to get enough current to the engine to either turn it over or operate the lift motor (faint click but that's it). Initially I assumed it was just a flat battery but replaced that and it made no difference. Have cleaned all the connections from the battery terminals, through the isolator to the engine and also temporarily bypassed the isolator but no difference. Voltage at the engine end of the cables is 12.6v - pretty much the same as at the battery. So to try and rule out a problem at the engine, I hooked up a battery directly to the engine (the normal battery location is in the console, roughly 4m ahead of engine with the power leads routed under the deck to the stern) and it fires up straight away and the lift motor works fine too.

So my only idea is that there is a problem with either the positive or negative cables running through the boat that is not a complete break but enough to prevent enough current being drawn to operate the starter / lift motor.

Before I go down the path of replacing these cables, could anyone more knowledgeable comment on whether my thinking is likely to be correct?

Also, suggestions on cable size / rating for an estimated 5m cable length that has to run from the isolator in the console to the engine and carry enough current for starting the BF90? Unfortunately I did not think to measure this when last with the boat and would like to order cable if that is indeed the problem.

Thanks

 

[stelican]

I have seen a similar problem caused by the isolator switch.
If yours is the type with a red remove able key try putting a piece of packing in the barrel of the switch and refit key which then puts more pressure on the terminals. Work for me a few times.

 

[VicS]

I have a 2004 Ribcraft 585 with a simlar age Honda BF90 that started fine 2 months ago but now seems unable to get enough current to the engine to either turn it over or operate the lift motor (faint click but that's it). Initially I assumed it was just a flat battery but replaced that and it made no difference. Have cleaned all the connections from the battery terminals, through the isolator to the engine and also temporarily bypassed the isolator but no difference. Voltage at the engine end of the cables is 12.6v - pretty much the same as at the battery. So to try and rule out a problem at the engine, I hooked up a battery directly to the engine (the normal battery location is in the console, roughly 4m ahead of engine with the power leads routed under the deck to the stern) and it fires up straight away and the lift motor works fine too.

So my only idea is that there is a problem with either the positive or negative cables running through the boat that is not a complete break but enough to prevent enough current being drawn to operate the starter / lift motor.

Before I go down the path of replacing these cables, could anyone more knowledgeable comment on whether my thinking is likely to be correct?

Also, suggestions on cable size / rating for an estimated 5m cable length that has to run from the isolator in the console to the engine and carry enough current for starting the BF90? Unfortunately I did not think to measure this when last with the boat and would like to order cable if that is indeed the problem.

Thanks

If you are measuring the voltage with no load then it will be the same as the battery but 12.6 is a bit low for a fully charged battery.

Try measuring it while cranking or operating the lift. If you then get a very much lower voltage it confirms the problem is somewhere between the battery and the motor.

Try also measuring the voltage drop directly on the positive and negative cables individually ( you'll need some extra long meter leads!) Then you should be able to see if the problem is in the positive or negative. Double check all the connections and the isolator based on what you find.

are there any hidden joints in the battery cables that may be causing the problem? For example between the original cables supplied with the motor and extensions.

Dont forget when sizing the cable that your cable run length one way is 5m but your total cable length is 2 x 5m.

I don't know what current your starter motor draws but I would be expecting 35mm² or perhaps 50mm² cables

There is guidance, and a calculator, for sizing cable in the "knowledge centre" on the 12 volt planet website. Also a sensible video.

 

[Oscar24]

I have seen a similar problem caused by the isolator switch.
If yours is the type with a red remove able key try putting a piece of packing in the barrel of the switch and refit key which then puts more pressure on the terminals. Work for me a few times.

Yep, had the same problem on my old rib. Ended up replacing two of them over 5 years ownership!
Them type of isolators are rubbish. They show a good voltage but as soon as you pull any current through them they fail.

 

[Davy_S]

Many years ago we had an old fishing boat fitted with an equally old Chrysler outboard motor, the engine did not have a conventional starter motor, but a dyna start system, we noticed that the motor was getting slower to turn over, until it failed to turn over at all, we had the dyna start wiring checked, but nothing was found, what the engineer did find wrong, was the battery cable hidden under the floor, he showed us the culprit, a six inch length of the positive cable had expanded and was acting like the element on an electric fire, it was a simple fix, and a lesson learned!

 

[stevecray]

Thanks all for your suggestions - a few things for me to check and hopefully pin down the cause

 

[Gemini]

On the actual lug termination there will be numbers IE 35 X 8 which indicates 35mm CSA cable and 8mm lug hole, 50 X 10 - 50mm cable with 10mm lug hole.

If copper core cable and the exposed ends have turned green, you may find the copper is breaking down with corrosion/reaction with salt atmosphere/damp causing high resistance.

The cables should be tinned copper conductors.

 

[Kawasaki]

I have a 2004 Ribcraft 585 with a simlar age Honda BF90 that started fine 2 months ago but now seems unable to get enough current to the engine to either turn it over or operate the lift motor (faint click but that's it). Initially I assumed it was just a flat battery but replaced that and it made no difference. Have cleaned all the connections from the battery terminals, through the isolator to the engine and also temporarily bypassed the isolator but no difference. Voltage at the engine end of the cables is 12.6v - pretty much the same as at the battery. So to try and rule out a problem at the engine, I hooked up a battery directly to the engine (the normal battery location is in the console, roughly 4m ahead of engine with the power leads routed under the deck to the stern) and it fires up straight away and the lift motor works fine too.

So my only idea is that there is a problem with either the positive or negative cables running through the boat that is not a complete break but enough to prevent enough current being drawn to operate the starter / lift motor.

Before I go down the path of replacing these cables, could anyone more knowledgeable comment on whether my thinking is likely to be correct?

Also, suggestions on cable size / rating for an estimated 5m cable length that has to run from the isolator in the console to the engine and carry enough current for starting the BF90? Unfortunately I did not think to measure this when last with the boat and would like to order cable if that is indeed the problem.

Thanks

Had the same
Buggered about with everything
Replaced the main cable from the control unit forward
Job sorted!

 

[Sneds]

Plus one for tinned copper conductors, get a TQ type cable and check it is tinned, plus when crimping the lug use some heat shrink

 

[Assassin]

I would use heat shrink with glue inside as the heat shrink shrinks and the glue is melted and seals the cable and its termination.

Have seen this many times, the corrosion transfers along the cable and at the weakest spot you start to get individual cores breaking and eventually they all snap and just touch each other, any movement and they part and you may get voltage, but little current, particularly when cranking, and the broken cores begin to arc and create more problems.