The Mark 58 inline 4 (the A is for Anniversary Edition) works exactly like
my venerable Merc 800 inline 6. I'm more than familiar with the procedure.
cough

Maximum spark advance and primary pickup are two different animals.

The Maximum advance stop should be when the piston is .235" before TDC -
It's not expressed in degrees in the manual.

The 1st pickup should hit just about when the timing crosses from retarded
(at idle) to TDC.

Then when the dist hits the max advance stop you want about .015 clearance
before the secondary pickup hit the carb cluster and begins to throw the
flutterbys open.

The sequence is.

Idle: Butterflys fully closed, timing retarded to give desired idle.

Then as you move the throttle, the timing begins to advance. When the timing
is no longer retarded the 1st pickup should hit and start to crack the
throttles.

Continuing on toward full throttle the timing will continue to advance till
it maxes out at .235" before TDC. Then...... a fraction of an inch of
movement later the secondary pickup hits the throttle cluster and it's all
carb movement from there.

-W (also recently bought a Mark 58 for use of a party barge when I get
older and wiser)



"Ignoramus11972" wrote in message
a.com...
This is for my friend.

He needs to interpret timing marks on the flywheel of a Marcury Mark
58A motor. What should be the maximum spark advance at primary pickup?

thanks

i