5.7L Voltage Gauge and Charging

scarpint

Petty Officer 3rd Class
Joined
Aug 25, 2008
Messages
89
My boat's in my sig line below. Story is haven't used boat this year until this past week and when I put it in, Voltage gauge was below 12V for most of that first ride out. Boat ran fine to begin with (battery fully charged), but when I got on plane for first time, it started to sputter. Got back to dock and worked with the "neighborhood mechanics" to eliminate fuel delivery issues and focused on electrical (focused on fuel as we didn't trust voltage gauge). All well (we think) with fuel pump with 6-7 PSI on the fuel pressure gauge. Anyway, noticed slip in belts and put on two new ones. Now, when started, voltage gauge is below 12v but slowly goes to 13v-14v as the motor idles. Takes about 30 seconds to do that. Will stay above 12v while running. Never gets over 14v. Boat seemed to run fine afterwards

Several questions: Is the gauge a reliable indicator of voltage and what is the normal voltage for this motor at idle, and does that voltage change with RPMS? If so, what should the voltage be at say, 3,500 RPMs?

Thank you for considering.
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
71,103
Re: 5.7L Voltage Gauge and Charging

My boat's in my sig line below. Story is haven't used boat this year until this past week and when I put it in, Voltage gauge was below 12V for most of that first ride out. Boat ran fine to begin with (battery fully charged), but when I got on plane for first time, it started to sputter. Got back to dock and worked with the "neighborhood mechanics" to eliminate fuel delivery issues and focused on electrical (focused on fuel as we didn't trust voltage gauge). All well (we think) with fuel pump with 6-7 PSI on the fuel pressure gauge. Anyway, noticed slip in belts and put on two new ones. Now, when started, voltage gauge is below 12v but slowly goes to 13v-14v as the motor idles. Takes about 30 seconds to do that. Will stay above 12v while running. Never gets over 14v. Boat seemed to run fine afterwards

Several questions: Is the gauge a reliable indicator of voltage and what is the normal voltage for this motor at idle, and does that voltage change with RPMS? If so, what should the voltage be at say, 3,500 RPMs?

Thank you for considering.

Ayuh,.... The volt gauge should go from battery voltage when ya turn the key on to 'bout 14v, 'n stay there while runnin',...

It usually take a few seconds above idle for the alternator to kick on,... Once chargin', it stays chargin' at 14v,...
 
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