Hello, 1st post here. I just bought a 1999 Glaston sx170 with a Johnson 115 on it. Everything seems to be working fine, the engine runs great however the tachometer will drop off somtime and will come back on after i throttle up. Also the voltage constantly reads 18 volts. Im not a boat mechanic of any sorts, i can do some automotive stuff. Any help would be appricated. Thanks.