First time out on the boat Saturday I noticed my alt gauge at cruise dropped around 12 volt with my Captain’s Call switch to loud…never noticed this before and it’s on my list to check out next weekend. It just so happens I was trying to get another year out of my 2016 batteries (which are on smart chargers always when @ home)…never a problem starting or even listening to tunes in a bay all day but I also remember those Corsa exhaust solenoids draw a lot of power. I can go grab some batts easy enough but is this a sign of an alternator problem? Any recommendation for an alternator from cp performance? Gm 502 was 454 mag in 1992 cobalt 243 Condurre.

I'll Take Both for $500 Alex

Could be as simple as the alt belt slipping. Check voltage at batteries and alternator and gauge with a volt meter.

Next time on the lake I’ll check it out…I did find a receipt for a new alternator during my 2017 rebuild debacle…purchased on eBay from romaine electric. Item# 272706630317 65 amp alternator for $67.83. Cheap alternator doesn’t make me feel any more confident but I’ll get my meter on it for sure. Thanks! Mercruiser calls for part #817119A4 BTW.

You can take the alternator into most Advance Auto stores, or the like, and they can test it for you. But if I could get my hands on a proper replacement alternator, and I was going through the motions of removing, I'd just install a new one anyhow.

What does your meter say with the Capt. Call off?

I say this because I have a Formula 292 Fastech with a Port/Stbd rocker switch that goes to my Volt meter. When I operated my CALL, the meter if on the Stbd side would go to 12 volts. But if off, would return to 14.5 Volts. Other 292 Owners have said the same thing. I load tested the Batteries and checked the Alts. All good. Called Corsa for amp pull and wiring diagram. All good. Called Formula for wiring Diagram other than their 1 line. Nothing from them. But I did check the resistance from switch to engine. Nothing that jumped out saying a problem.

So I installed a electronic relay under my dash and had a spare CB IGN spot to install a 20 amp CB. Will change the IGN to CORSA on the panel later. This fixed the problem. Now when the CALL is on, both Port/Stbd show actual voltages.

I replaced the 5 year old batts for peace of mind and I snugged up the belt a bit…1200 idle voltage at alternator is 14.6v…at back of gauge is 13.2…the gauge is showing a bit erratic.

Just a guess…. power supply problem. Wiring to helm feeding ignition switch or from ignition switch to gauges is to small. Follow the circuit with a voltmeter and see where it drops off.

Good luck with that! Unless you happen to have someone there that actually knows what they are doing these stupid kids dont know chit unless its on a computer screen! Last time i took an alt into local advanced auto and asked to test it first question was "what cars is it from?" um its not off a car but you can test it just the same....he looked like a computer stuck in reboot....then he tells me unless they know what its from they cant test it as they need to tell the system what its for.....
Seriously? so now the alt testing machine is so sophisticated that it has to know what its from to be able to test it? Left and took it to a place that rebuilds starters/alts....didnt even have to say a word other then can you test this...he said yup and took it to the back....3min later comes back and says she is all good must be something else causing issues....

I had the same exact experience.