Mercury 115 low charging voltage - already replaced parts

[Bshifty]

On my 87 115 inline 6 Im having a charging voltage issue as well as the tach reads 4k rpms at idle or with battery off. Charging voltage is 12.08vdc
I have placed the following in this order thanks to my mechanic. Rectifier, Stator, switch boxes then the rectifier again, Batteries are fresh,Its also tough starting when cold. This all started around the time my trim tilt pump was replaced be the same marine mechanic, Help ...

 

[Maxz695]

Re: Mercury 115 low charging voltage - already replaced parts

Mechanics love to guess and change as many parts as you will allow them too. $$$$$ Cha $$$$$ Ching!!! Try checking the grounds on your instrument panel especially the Tachometer ground. While your at the harness check for spliced wiring. Any spiced wire with wire caps or tape should be redone. The spliced area is prone to corrosion after time and bad connections are the result

 

[Bshifty]

Re: Mercury 115 low charging voltage - already replaced parts

Mechanics love to guess and change as many parts as you will allow them too. $$$$$ Cha $$$$$ Ching!!! Try checking the grounds on your instrument panel especially the Tachometer ground. While your at the harness check for spliced wiring. Any spiced wire with wire caps or tape should be redone. The spliced area is prone to corrosion after time and bad connections are the result

Thanks for the reply, I have checked for splices, There is a red wire going to one of the switch boxes that had some jacket missing, copper was fine, i taped it, I used a meter on the battery to check for charging voltage. I also tried metering different ground spots on the motor to battery ground and had continuity. As far as the tach reading 4,000 with the batterys "off" I think the tach is toast. I think I made a mistake boosting the battery with a charger on start mode