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RPM Signal

T

Tedder

New member
Hello,
I have a 1991 Mercury 135hp Blackmax outboard. It runs great but I am not getting a signal back to my rpm gauge. I have ohmed out the wire and it is fine. This motor uses a voltage regulator, not a rectifier, he voltage regulator is fairly expensive. Is there an alternative to read my motor rpm's other then replacing the regulator to send a signal through the grey wire back to the gauge?

Thanks in advance.
 
Had similar experiences. If this is not a Merc voltage regulator (or Merc didn't do its job right) then this will happen since the tach is looking at the AC voltage coming from the stator.

The voltage regulator 'cuts off' the flow of amperage (so to speak) to prevent over charging the battery. When that happens the tach receives a less than needed signal and stops working.

There's two ways around this:

1. Buy a CDI voltage regulator that has a gray wire for the tach. Inside the unit, electronic trickery keeps the tach receiving a signal regardless of what the battery needs are.

2. Eliminate the voltage regulator and run with the rectifier only. I do this with my older Mercs, which were designed that way (and don't over charge the battery too much).

Jeff
 
fastjeff said:
Had similar experiences. If this is not a Merc voltage regulator (or Merc didn't do its job right) then this will happen since the tach is looking at the AC voltage coming from the stator.

The voltage regulator 'cuts off' the flow of amperage (so to speak) to prevent over charging the battery. When that happens the tach receives a less than needed signal and stops working.

There's two ways around this:

1. Buy a CDI voltage regulator that has a gray wire for the tach. Inside the unit, electronic trickery keeps the tach receiving a signal regardless of what the battery needs are.

2. Eliminate the voltage regulator and run with the rectifier only. I do this with my older Mercs, which were designed that way (and don't over charge the battery too much).

Jeff
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Thank you for the info. I will look into both solutions and see which I can make work.
Ted
 
If it has the 40 amp 1 piece water cooled voltage regulator make sure it has 12V on purple wire at regulator when key is on. If so and still dont work bite the bullet and convert to 2 regulator set-up. yes its expensive as stator has to be changed also.
 
Thanks, I'll get out there and check it today.
The stator was another thing I was going to check, I haven't done that yet so it's time to get the multi-meter back to work.
 
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