Battery or alternator?


Baycation

Baycation

New member
Hello All,
My first post here but I have been reading posts for some time. I just purchased my first Formula. It's a 2006 gulfstream blue 330ss w/ 496s and I love it. I'm working out a couple of minor bugs. After my first couple of short test trips I noticed the starboard engine became hard to start and eventually wouldn't start without turning the parallel battery switch. Once started I would switch the parallel switch off and the engine would run fine. The volt meter on the dash shows 12.3 volts. I put a volt meter on the battery and show 12.73 volts. I took the battery to two shops for a bench test and both show 12.7 volts but also note to replace the battery. I replaced the battery and everything works fine but the volt meter on the dash still shows 12.3 volts. The volt meter for the port engine shows 14.3. Do I have an alternator going bad? Also note that I store the boat in a boatel with the battery switches off and no shore power allowed to run the charger.
Thanks!
 
So I checked the voltage at the battery with the engine running. 11.4 volts. It must be the alternator. Now I'm shopping for a new alternator and find prices ranging from list of $340. to a low of about $80 bucks. I'm thinking I should stay with the best deal I can find on a black OEM unit for about $265. Anyone use the $80 units?
 
Baycation said:
So I checked the voltage at the battery with the engine running. 11.4 volts. It must be the alternator. Now I'm shopping for a new alternator and find prices ranging from list of $340. to a low of about $80 bucks. I'm thinking I should stay with the best deal I can find on a black OEM unit for about $265. Anyone use the $80 units?
Click to expand...

Don't do that just yet. You either have a battery isolator or an ACR (Automatic Charge Relay). Formula likes using isolators because they work and are easy to install. If an isolator is used the output of the alternator output terminal send voltage direct to it. Then depending on how many banks are used, it then sends it to the batteries. There is a .7V drop going thru the isolator.

Isolator is normally mounted near the start and house batteries, and has a finned aluminum housing.
 
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