1979 Mercury Mariner 80 hp timing issues

[jschurz]

I'm trying to set the timing on my motor (serial #5385921), but I guess I just can't follow the directions correctly. I'm doing it with the 2 - 4 spark plugs grounded, the throttle cable unhooked, and TDC was found (using a piston stop tool) at 0 degrees. I've read the previous posts on the topic, and the directions posted by SpinnerBait_Nut. On my motor the throttle arm first goes to something labeled spark stop. This is the point where the cam contacts the carburetor. Is this the same as primary pickup? If so, instead of seeing the 2 or 3 degrees before TDC with the timing light while cranking the engine at this point, I saw closer to the 27 degrees for max advance that the manual says I need. When I moved the throttle past spark stop, the timing didn't seem to change at all when looking with the light. I could only see the 2 or 3 degrees before TDC with an adjustment of the idle stop screw. Thank you for any help you can give!

Jeff

 

[jschurz]

So, I've figured out that max. advance is the same as spark stop, and I can get the correct timing adjustment (27 degrees) for it. Now my only problem is getting the correct adjustment with the primary pickup screw. I move the throttle lever until the butterflies begin to open, then while holding the throttle arm steady, I'm supposed to adjust the primary pickup screw until I reach 2 degrees before to 2 degrees after TDC. Even if I turn the screw all the way in it won't get to 2 BTDC.

 

[Chris1956]

You might check to see if Merc updated the max spark advance and idle pickup timing specs. I had thought max advance was changed to 21*BTDC. A normal ADC idle pickup timing is 0-9*ATDC.

 

[jschurz]

Where would I find updated specs? I just got these from my Seloc manual. Should I time my max spark first, then try and get the 9 degrees for the pickup? It just seems strange to have that pickup screw all the way in to try and reach it. Also, is BTDC to the left of 0 as you look on the flywheel or the right? Thanks a lot for the help. I realize this topic is like beating a dead horse on this forum!

 

[jschurz]

One more question... Should the engine be in neutral or forward when timing?

 

[Chris1956]

You will want to set the timing, with spark plugs 2-4 removed, installed into their wires and their bases grounded. Remove prop as well. Install timing light on top spark plug. Put motor in gear and jumper the starter (ign on), and advance the throttle until you see 0-9* ATDC. Now set idle pickup timing screw so the carbs are just ready to open. Now advance throttle fully and crank motor. Adjust max spark advance to be 21* BTDC. Set throttle stop so carbs are fully open, just at their stop.

Now install prop and plugs. Put boat in water and set idle speed to 900 RPM in neutral. She should idle in gear at about 650-750.