Just had motor r/r. Not charging...so I put in a new alt...hooked up exactly as original. Now it shows 12v at idle and 10v at hi idle....what gives.

Oh...454 magnum 97

Check water in your Batt.'s sounds like you got a cell down.

+1 or just a bad battery..

I have a 88 Formula with a 454 Mag and it started doing the same thing one day. It drops to 10V at 5K but will pull 12V until 3K before it starts falling off at the higher Voltage does the same on each battery or on both.

Tried 4 dif batts...same story.

Bodi...so what did you do....

ok did you replace the belt? could be slipping..

Possible...but would a loose belt make the gauge go down as the rpms go up?

Gauge drops 2volts

Possible...but would a loose belt make the gauge go down as the rpms go up?

Gauge drops 2volts

Whoops...sorry for the show post