Voltage drop

Joined
Jun 25, 2012
Messages
7
Hoping someone can shed some light on my issue. I have a 5.7L merc with thunderbolt IV igition. When running at idle the voltmeter reads 13V except when a give it a shot of fuel in neutral. The voltmeter drops to 11V. Is this normal?
 

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,093
Re: Voltage drop

nope, not normal to jump lower or higher. The Mando ones like to get loose wiring problems at hi rpm`s
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Voltage drop

No, sounds like your alternator isn't working or the belt is loose, or corroded connections......... No, it's not normal, should increase voltage as you increase the rpm.
 

Reel Poor

Vice Admiral
Joined
Jan 29, 2005
Messages
5,522
Re: Voltage drop

You may have a weak battery and a loose alternator belt. If you can turn the alternator pully by hand, with the belt installed, the belt is to loose.
 
Joined
Jun 25, 2012
Messages
7
Re: Voltage drop

So I tried turning the pulley and I could. I will put on a new belt a give that a try. Could low voltage be causing engine power loss. Yesterday I had the boat in the water and it wouldn't get up on plane, the engine seemed to be struggling for power.
 
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