volt gauge off chart

[bigbillone]

I have a 2001 f115 on a hurricane deck boat , battteries went dead after many years . put two new ones in ( connected to batt switch ) perko 1-all-2 . at idle volt gauge 12.- above idle goes to 16 volts and stays pegged . is it the rect/reg ? how do i test it ? also tach quit some time ago is it related ? or completely seperate ? rec/reg back side looks like it got hot . also 1 terminal black and discolored .
Thanks for your input
Bigbill

[zenoahphobic]

You probably answered it yourself. If the voltage is 16v DC immediately at idle, together with burnt appearance, first thought, would be your regulator probably faulty.
Hard to compare AC volts reading before the regulator with the DC reading coming out. But you can actually see if it is actually DC by disconnecting it and seeing the reading on a multimeter DC setting (DC would fluctuate around zero if it was AC).
I mentioned this because AC (which is not wanted) across a fresh battery can actually raise "voltage" as interpreted by some meters. And this depends on the type of meter and where it is actually reading this voltage.
The other thing you can do is put back the old battery(s) and see if it will also charge them to 16V. If the latter is so then your regulator is faulty or it always has been high (14.5 should be max), but hasn't affected the life of your last batteries (presumably they are constantly being used and spend less time at fully charged state - where high voltage would actually damage them).
Did you measure with the meter probes directly on the lead parts of the battery terminals?.