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Ignition at idle

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MartinArgentina

New member
Hello dears. I'm adjusting the ignition on my 1979 Mercury 3 cylinder 70 hp. I'm asking if you know how much advance it needs at idle.
Thank you so much.
Greetings.
Martin.
 
Hello Racerone. I removed the clearances that the acceleration command had. I thought it would be good to check the ignition advance, since from what I see it has a registration screw for idle and another for maximum throttle.
 
Not familiar with your engine. At idle the crankshaft is spinning slow enough that TDC or a few (single digit) degrees will suffice in spark advance on most engines. Once up and running, at 5000 RPM give or take you will need 20-25* BTDC spark advancement and the engine should provide that for you with the spark advance lever that is connected up under the flywheel will accomplish for you.....you can see it move when you advance the throttle and see what moves.....there is carburetor butterfly movement and there is movement up under the flywheel, possibly by the same arm connected to the throttle remote cable termination in the engine proper.
 
Hello Texasmark. Indeed, the advance is in solidarity with the movement of the carburetor butterfly. With maximum throttle, I adjusted the advance to 21º. For idling, the acceleration and advance system are at rest and have a registration screw for regulation. I found that in that state, at idle, the spark is delayed by 6º. Could it be?
 
Not uncommon for some ignitions to have no advance timing at idle. That is, idle RPM timing might be X degrees after tdc. Top Dead Center.

The specification and the procedure will be found in the applicable Mercury Marine service manual.
 
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