idle stabilizer on 1985 outboard 90 hp L6

[crossland]

I have an 1985 mariner 90 horsepower L6 which has something called an “idle stabilizer” . I believe that this device senses when the motor runs below about 550 RPM and then sends a bias voltage to both CDI boxes to increase the spark advance ,

The net effect is that at low rpms the “idle stabilizer” sends a voltage to a particular terminal on both cdi boxes which increases the spark advance and makes the motor run smoother and stronger at low speeds .

I think my “stabilizer” is dead and mercury / mariner no longer stocks “idle stabilizers”

Does anyone know the output bias voltage of the “stabilizer? is it 3 volts ? 4 volts? 2 volts ? On a working motor is the bias output voltage always the same ? Say for example is it always 3.2 volts ? Or does the bias voltage vary with the engine RPMs . Say 2.8 bolts at 550 rpm but 3.5 volts at 500 rpm . My low speed idle is rough and weak – I want to try to jury rig a manual voltage input to the CDI boxes so I can get better low speed performance from my motor .

[billw]

Your questions are way above my pay grade. However, many inline sixes were made with NO idle stabilizer and were fine. There are a lot of reasons they won’t idle smoothly and reliably, like flooding carbs or the loss of compression or spark on one cylinder. The biggest thing, by FAR though, is also the simplest to fix. All three carb throttle plates have to crack open at the EXACT same time. Over time, the plastic links between the carbs grow weak, which results in progressive throttle lag between the top, middle and bottom carbs. You can readjust the links to correct for this. I don’t know how many times I did this simple adjustment and made a lousy-running engine run like new.

Long live American manufacturing!

• This reply was modified 5 years, 8 months ago by billw.

[Arthur Taddei]

Remove the stabilizer and raise the Idle screw 100 RPM’S Mercury had us Techs remove them cause they would malfunction and advance the timing at wide open throttle ,resulting in a detonation in No# 1 or 3 cyl

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