New alternator, still low voltage

[MarcelSydney]

Hi all.
1999 Maxum 1800 with a 4.3L V6 Mercruiser. Serial numbers are OL323311 (engine) and OL509362 (Transom).
I have been getting low voltage from my alternator. 12.3v. In the last few months I've put a new battery and new starter. Cleaned battery terminals.
I had a leaking power steering hose and it coated the alternator, figured maybe it was ruined.
Replaced it with a new one tonight, and still only get 12.3V??

I noticed that the helm voltage gauge isn't registering voltage either.

Any ideas of where to start looking? Maybe a bad ground on the engine block?
Is there something obvious I'm missing?
Thanks a lot

 

[jimmbo]

Are You just going by the Dash Gauge, or have you used a Multi Meter to measure the Voltage at the Battery, Alternator, and any connections in between?

 

[MarcelSydney]

multimeter. Measuring at the battery terminals and alternator.
Dash gauge is an observation, can't help but wonder if it's related to whatever is going on.

 

[jimmbo]

Have you tested the Voltage Drops along the Circuit?
What is powered, that draws a large Electrical Load?

 

[alldodge]

Bat and ALT measures 12.3V
It's either the ALT or the wiring

The ALT has 3 wires, orange main power, red/purple since, purple excite

Orange = Bat voltage, should read same on starter post
red/purple = Bat voltage with key ON or OFF
Purple = Close to Bat voltage with key ON and 0V with key OFF

If voltages are correct than it's the ALT

 

[Scott06]

Is the idle speed too low do you get higher volts when engine revs a bit?

 

[Bondo]

Hi all.
1999 Maxum 1800 with a 4.3L V6 Mercruiser. Serial numbers are OL323311 (engine) and OL509362 (Transom).
I have been getting low voltage from my alternator. 12.3v. In the last few months I've put a new battery and new starter. Cleaned battery terminals.
I had a leaking power steering hose and it coated the alternator, figured maybe it was ruined.
Replaced it with a new one tonight, and still only get 12.3V??

I noticed that the helm voltage gauge isn't registering voltage either.

Any ideas of where to start looking? Maybe a bad ground on the engine block?
Is there something obvious I'm missing?
Thanks a lot

Ayuh,....... You need to clean Both ends, of Both battery cables,...

 

[Scott Danforth]

By clean....use 150 grit and make the terminals shiny enough your mother in law would eat off them

If the cables are crunchy, replace them

When done, seal the connections with marine electrical varnish

 

[cyclops222]

Is your idle speed too low ?

 

[alldodge]

The guys bring up a good point. If motor starts and idles at 700 rpm then the ALT may not start producing power. Motor needs a quick rev (about 1500) for split second then back to idle

 

[MarcelSydney]

Thanks all.
I'll check the other end of the cables.

Yep, even at around 2000rpm, no increase in voltage.

 

[jimmbo]

What is the Voltage of the Battery, unhooked? And after it is charged with a Battery Charger?

 

[alldodge]

What is the Voltage of the Battery, unhooked? And after it is charged with a Battery Charger?

After resting off charger for a few hours
Lead acid 12.7
AGM 13.0

 

[cyclops222]

Is it possible you were sold a defective new Alternator ?