2006 yamaha 150 four stroke charging problems

[davindyson]

I have twin 150 yam 4 stroke on center console.After starting both motors I observe only 11.6 volts on gauges and batteries will not stay charged.I check voltage output at batteries and it is 11.6 volts.A mechanic told me that you have to have good batteries for charging system on motors to engage and alternator to properly put out 13 or so volts.I also checked voltage at starter on motors and it is same-11.6 volts.Please advise...

 

[Shermanator31660]

Not sure about your alternators but mine put out over 13 volts whether the battery is dead or not! I'd be putting a volt meter on your alternator and see if its even putting anything out first and then go from there. Poor batteries won't hold a charge and if a couple of the cells have "welded" together from the sulfates it may give a wonky reading on your gauges. That or take the batteries out and try them on a battery charger and see what you get........Sherm

 

[ggirf14]

Checking charging system with a dead battery (11.6 volts) open the door to false diagnostic. Slow charge the battery is always the best but 15 amps charge would be an ok alternative. A charging system will push 14 - 15 volts and should cut off over this to avoid damaging the battery. when you unplug the charger check the voltage drop every 15 minutes. It should stabilize within 2 hours. Once there the final voltage should be 12.1 (empty) to 12.8 (fully charged). If your battery is fully charged you can turn on accessories to draw current to check the charging system. If the voltage stays over 13 volts it you are in business. Keep turning accessories on until you reach the limit of your charging system.

Notes:
- A faulty battery may require charging like crazy (short) or may be low and not accepting any amperage (open circuit or sulfated).
- Lead / acid batteries are technically discharged @ 12.1 volts and fully charged @ 12.8 volts (stabilized voltage).
- A basic digital volt meter is a must.
- Auto parts retailer often have volt meters in 20.00$ range that are accurate enough to do the job. 100.00$ multi-meters would be an over-kill.