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TOPIC: How to set Max. Timing Advance on Mercury Mark 58.

How to set Max. Timing Advance on Mercury Mark 58. 2 years 7 months ago #130215

I thought I would share how I set the maximum timing advance with a standard VOM meter, after the initial timing has been set. Be sure to follow each step in the Mercury Services Manual when doing the lynch & Synch. Top dead center can be found on #1 cylinder with a timing gauge or with a dial indicator through the spark plug hole. Once TDC is reached, zero out the dial indicator and make sure you have at least 3/8" travel inward on the indicator shaft. With all the spark plugs removed, rotate the flywheel counter clockwise slowly until the dial indicator reads .235. Do not rotate the flywheel after setting at .235 before TDC since this is the correct flywheel position to set the maximum timing advance. The lower portion of the magneto must be un-bolted from the upper section. There are 4 bolts that hold the two sections together. Once loose the lower section will slide down for removal from the spline shaft. Note the position of the flat on the shaft. The magneto shaft will have to be in that same position to go back together. Loosen the 4 screws that hold on the magneto cap and carefully remove it along with the gasket and grounding strap. Next remove the cap with the spark plug wires, along with the rotor. It should slide easily off the shaft. Both the rotor shaft and magneto shafts have flats so they can only go together one way. Do not force anything. Now it is time to remove the coil wire and condenser wire from the points post. Leave the wire that goes to the insulated magneto grounding terminal on the points post. That will be the only wire connected to the points for setting the max. timing advance. I wrapped electrical tape around the coil wire and condenser wires that were removed to keep them from grounding out. With the magneto on the test bench, turn the VOM meter to ohms. Place 1 wire against the magneto insulated ground terminal and the other against the magneto housing. Rotate the magneto shaft and watch the meter. You can now see on the meter when the points close. Next is to install the lower magneto section back onto the upper magneto. Righted the bolts and then you are ready to set the max. timing advance. Loosen the 2 bolts that hold the slotted bracket to the side of the magneto. Now rotate the magneto and watch your VOM meter for when the points close and hold the magneto in this position while rotating the slotted bracket until the rubber stop is against the block and tighten the bolts on the slotted bracket. Release the magneto and then rotate it against the block and verify the points close when the rubber stop contacts the block. Now your max. timing advance is set. Remove the lower magneto section again to reconnect the coil and condenser wires to the points, put the cap back on, them rotor and rotor cap. Be sure to reconnect the ground strap and the 2 wires going to the insulated terminal. Now you are ready to make the other 2 carb. Settings. Please refer to the manual for that procedure. I hope this helps.

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