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Electrical problem with Yamaha 15HP 4-stroke outboard

SteveDH

Member
Joined
14 Aug 2014
Messages
46
Location
Reading, Berkshire
Hi All,

Is anyone able to give me a few ideas on an electrical problem I have with the 2004 Yamaha 15HP outboard on my RIB?

All was good when we stored the RIB in the autumn, but on trying to start her today (electric start), she appears dead. The battery is charged (to 12.8V), but as soon as I turn the ignition to stage 1, the battery voltage drops to 4V as if something is dragging the power down.

An accessory supply from the ignition comes into the steering console which powers a GPS speedo and some LED nav lights, but I've disconnected this supply to rule out a problem with these accessories, and the problem still exists.

The positive and negative cables run from the battery straight into the outboard, and the 12.8V is good there. As soon as switch the ignition key to stage 1, the voltage drags down to 4V and everything appears dead … no clicking or any signs of life, nor any cranking if I move the ignition key to the cranking position.

If I switch the ignition back off, the battery voltage lifts back to 12.8V.

Any suggestions as to what to check first?

Thanks in advance

Steve
 

longjohnsilver

Well-known member
Joined
30 May 2001
Messages
16,637
I’d be checking for corroded electrical connections first. And make sure they’re all tight.
 

SteveDH

Member
Joined
14 Aug 2014
Messages
46
Location
Reading, Berkshire
Do you know what - it just might be. It's a brand new battery and the fault wasn't there when we parked her up in October. I've only changed the battery on her (nothing else) and the fault is now present, but the battery came charged to 12.8V out of the box, and is still out-putting 12.8V until the ignition is switched on.
:unsure:
 

Assassin

Well-known member
Joined
23 Jun 2010
Messages
1,157
When you crank the engine the voltage shouldn't drop below 9 volts and if it does there isn't enough power for the ignition system.

Get the battery drop tested as they can show 12.8 volts when new, but cranking puts them under load and this shows defective batteries.
 

SteveDH

Member
Joined
14 Aug 2014
Messages
46
Location
Reading, Berkshire
When you crank the engine the voltage shouldn't drop below 9 volts and if it does there isn't enough power for the ignition system.

Get the battery drop tested as they can show 12.8 volts when new, but cranking puts them under load and this shows defective batteries.
Thanks, but this doesn't apply to my problem ... there's no cranking ... the voltage drops to 4V the second the ignition key is switched to stage 1.
 

gordmac

Well-known member
Joined
28 Jan 2009
Messages
8,453
Location
Lochaber
Bad connections and/or knackered battery. If the battery is new can you take it back under guarantee for a check? Can you try jump starting it? Can you run decent jump leads directly from the battery to the starter? Can you use a decent jump lead from the battery earth to an earth point on the engine?
 

SteveDH

Member
Joined
14 Aug 2014
Messages
46
Location
Reading, Berkshire
Just thought I'd feedback in case it helps someone else … it was the positive battery lead. Insulated sheath of the cable was in good shape, but most of the strands within the positive cable had corroded inside.
New cable on its way!
Thanks for your help!
 
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