1975 Merc 50 tach question

[wiggles6983]

I have a 75 merc 50. I wired a new tach up to the rectifier (on one of the 2 wires coming from the stator, and the dial on the tach is set to 6 pulse (12 pole). At idle the tach jumps from 0-500ish very randomly (engine sounds to be idling fine), if i increase to high idle it settles down and seams to be very accurate.

Now my questions is, is the idle reading normal, if not what can I do about it?

Chris

 

[Laddies]

Re: 1975 Merc 50 tach question

Switch to the other yellow wire at the rectifiier to see if the rectifier is or the one side of the stator is shorting. If that don't help you have a bad tach

 

[wiggles6983]

Re: 1975 Merc 50 tach question

I haven't gotten to change the signal wire over, but when i took it out yesterday my voltage gauge was showing 16 volts at 5k rpm. Is the rectifier going out?

 

[wiggles6983]

Re: 1975 Merc 50 tach question

Switched the wire and have the same results.