Charging system ?

[Justjoe]

Hi I have a 1977 35hp evinrude. When the motor is running and I check the voltage at the battery I'm getting 16 to 18 volts sometimes it spikes to 20 it's very intermittent. Is this normal or is this an indication that the rectifier is bad?

[boats.net]

That engine doesn't have a voltage regulator just a rectifier so can see high voltage, make sure battery cable connections are clean and tight.