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89 Mercruiser 57 260 Alternator

R

rudder

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"Took boat out of storage yest

"Took boat out of storage yesterday for maiden voyage of the season...bought new battery, as old one was 5 yrs old..started right up...burned off fogging oil and flushed anti-freeze out of cooling system, ran great...once on Lake Tahoe, voltmeter stayed low, 11-12 volts throughout rpm range, for the 3+ hours we were out...I did notice kids had all four auxiliary lights on, but didn't seem to make much difference once we turned them off. Any ideas where to start..I do have the Mercruiser manual...will start troubleshooting per the Mando Alternator tests. I believe the alternator is original."
 
I'd check the battery volt

I'd check the battery voltage while running with a meter at the battery.It should be in the 13.5-14volt area.Then check battery voltage not running and it should read in the 12.5 volt area on your meter.This will give you somewhere to start.
 
"Battery voltage when running

"Battery voltage when running at 1,500 rpm is 14.58 vdc...with engine off 12.9...dash volt meter reads 12.5 vdc at idle, then drops to 12 at same rpm. Maybe gauge is bad...everything else seems to be OK..."
 
"does any of your other gauges

"does any of your other gauges bounce or move when you throttle up, if so check the connections on the back of the ignition switch. I just went through the same problem where every place I checked the voltage was correct yet the gauge read 10 to 11 at around 200 RPM. you can also check the back of the gauge you should have either a red wire or a purple wire and then a black (ground) in the center check your voltage there to see if it is your gauge.."
 
"As bill says you probably hav

"As bill says you probably have a loose wire,or a bad gauge as you say.The readings you gave from the battery are normal so your alternator is working alright."
 
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