Bad Voltage Regulator???

[<Jokerswild5>]

To start - I have a 97 225hp yamaha saltwater series OB. I suspect I have a bad volt reg, but I wanted to get a second opinion before purchasing a new one. The conditions that i'm getting are, 1)no engine rpm readings, but the other functions of the gauge are fine. 2)batteries were "dead" only after sitting for a week. 3)while underway, when i trim the motor and/or tabs, my voltage readings go from 13.2 down to just under 10v-depending on how long i utilitize the controls. The batteries were replaced last summer, and they do hold a charge while out the for day. Any comments or advise will be greatly appreciated. Thanks in advance...

Nick aka Jokerswild5

[<boats.net>]

Sounds like you possible have wiring problem, bad battery connection,battery's, bad ground or cables.
If you are getting 13.2 Volts, then it is probably charging. Have the battery's tested,wiring and tach checked first