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Timing Help

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rmcderm313

Regular Contributor
Hi All,

Could someone help me with some instructions on setting the timing on a 1987 25 HP Merc? I understand the concept of timing, and I know how to connect the timing light, but I'm not clear on where I'm supposed to be shining the timing light. I have the service manuals but they just say "using the proper procedure" check the timing.

photo 1.jpg

If there is a good resource to read somewhere that would be great.

Thanks,
Rob
 
Connect a 12 volt battery to the timing light, and ground the negative terminal of the battery to the motor. Then away you go.

You will have to remove the carb's throttle linkage so you can hold the motor wide open.

Jeff
 
Your photo there shows the side of the powerhead.

Around the front, just above the carb where you can see the flywheel there should be a pointer (like a finger) up near where you can see the timing marks.

You point your timing light there and the (strobe) flashing will "light up and freeze frame" those timing marks/dots - then you simply adjust the linkage etc to move the mark you want directly over the (finger)...
 
Thanks Guys, I think I'm getting it. A few more questions...

From what I can tell the single way to advance or retard the timing on this motor is by lengthening or shortening this rod which is connected to the trigger.

IMG_2687.jpg



kimcrwbr1, It sounds from your explanation that there are two different timing adjustments, throttle pickup and WOT. Are these modified in two different ways, or are they both set by modifying this rod length, just doing so at different engine speeds. Do I need to run the motor at WOT to read the timing? or is this supposed to be done just while cranking the engine?

When you say "adjust the idle speed to 700RPM" how do I do that? Are you talking about the idle mixture screw? I haven't yet been able to get the idle down below around 1200RPM.

Thanks for your help all,
Rob
 
Throttle " pick-up " is not a timing adjustment !!-------It is the point where the throttle starts to open.----This means that it is a carburetor / linkage adjustment.
 
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