Johnson losing voltage

[Lt_Nutz]

Looking for ideas on where to start. 2002 115 Johnson 2 Stroke appears to be losing Volts. Gauge typically reads 14V. Now fluctuates between 13-12V. Mostly 12V or below. Just tested the battery after last trip and it reads only 2/3 charge. Traced all connections, cleaned battery connections. All appears in order. Engine starts and appears to run normally. Any suggestions before I start replacing parts $$$???

Don't know if it is related. Older Raymarine L365 fish finder lost about 1/8 column on the display after last trip. Today it lost about 7/8 of the display.

Thanks in advance.

[seabob4]

Diode on the alternator shot?  When off, will drain a batt...

[GoneFission]

Agree with Bob - check charging output on mota - then check the batt - could have a bad cell...

[Lt_Nutz]

I had the battery tested and it was bad.  New battery installed and fired up the motor on the trailer with the ear muffs. Gauge reads 12 Volts at idle. I don't have a voltmeter yet to test the engine output. Is 12V at idle with a full battery normal? I get along with my neighbors so I don't want to run up the RPM's in the driveway.

[GoneFission]

Somewhere around 12 volts might be about right at idle - you need to take it out and run it a bit to check it out - but I'll bet the new battery fixed your problem.

[seabob4]

Nutz,
I just did a job last week, one of the owner's issues was that his voltmeter was reading just under 12V.  Put my meter on the terminals on the backside of the gauge...checked 12.24V rest voltage.

Don't trust your voltmeter on the dash...

[Lt_Nutz]

Just picked up a voltmeter. Starting back into my work week so it may be a few days before I can get out on the water. Until then I will test what i can, clean the engine connections and report back with the results.

Thanks for the responses and advice !  

[Capt. Bob]

Don't trust your voltmeter on the dash...

What the f....?
Again I have to agree with SB. 8)

Not popular.
Looks OK with digital instruments :|
Works great and is extremely waterproof.

http://www.datelmeters.com/cgi-bin/webs ... eacdc.html

Just sayin'

[Lt_Nutz]

I am back finally. Truck broke down and had to be fixed first.

New battery installed inboat. Fully charged. VM reads 12.58 at battery and at solenoid. Engine running after instal read 13.7.  I then took the boat out for a 3-4 hour trip.  VM on dash and on new fish-finder read 12.4 volts. Twice that I noticed it went up to 14.7 when RPM's were up but not for a long period. Then back to 12.4.  Back in the driveway i removed and cleaned every connection I could find. Inspected every wire and connection. It is reading 12.5 at battery and at solenoid (both sides). Running it drops to 12.4 again.  Tested after idling for a bit and it tests 12.48 with engine off now.  Engine appears to be running normally otherwise.  Am I back to normal and it's sending no charge to battery because it is full? Or should volts be up  at 14 all the time.  I seem to recall the Voltmeter on the dash reading 14 ALL the time in the past.

[Capt. Bob]

Am I back to normal and it's sending no charge to battery because it is full? Or should volts be up  at 14 all the time.  I seem to recall the Voltmeter on the dash reading 14 ALL the time in the past.

I can only speak for my 96 Evinrude and my 91 Yamaha so...

Both had "regulated" charging systems that are designed (within engineered specs) to supply a given amount of voltage at a given rpm.
That stated, my Yamaha has a 25 amp system that, when in spec, supplies in the range of 14.2 to 14.6 volts at 3500 rpm. With aging, the voltage can vary and I've seen it approach 15 volts while underway so...
With a good voltmeter, you should see the charging output of your motor while underway. Remember, as electrical requirements are being met, that voltage may vary but once everything is settled in (you're cruisin' with the GPS and sounder functioning but not washing down the deck or maybe talking on the VHF) your voltmeter should show a fairly consistent range based on the charging system's designed output.

I'd think you should be reading in the 14+ volt range at your cruising speed (3800 to 4200rpm I'm guessing). If you are reading 12 volts, then the system is either undercharging or your gauge is not reading correctly.

[Lt_Nutz]

While underway with RPM's over 4000 it was consistently 12V on the dash gauge. Lowrance fish-finder has a built in voltmeter that read a fairly constant 12.4 volts also. Turned on all other accessories (radio, pumps, lights) and volts dropped to 12.3 to 12.2. Only twice that I observed did the volts go up to 14V+ on both gauges while underway with RPM's up. And it was only up for a short time.  

[Lt_Nutz]

New voltage regulator installed. Problem fixed!