ignition timing

I have a 72 mercury 1150, can someone help me to understand exactly what this means.

"When the throttle is in the idle position the carbs should be fully closed and the ignition retarded. It is the amount of retardation that determines your idle speed and is set later with the idle stop screw."

when it says ignition retarded is that 0 deg? right now I have mine set at 0 deg when the throttle is in neutral, 4 deg primary advance, secondary advance just touching before economizer collar, 21 deg max advance

any help would be great, thanks, J

Re: ignition timing

I think what they're trying to say is that while all the other settings above idle are very specific as to what they have to be, the at-idle timing is going to depend on the particular running characteristics of the motor.

In other words, it's gonna idle where it's gonna idle, and once you've got your best idle, warmed up in fwd gear in the water, and adjusted the "idle stop", if you put a timing lite on it it's gonna be what it's gonna be. With all the other parameters set up correctly, it'll probably fall in the range of say, around 4 deg ATDC to maybe 0 deg (at TDC).

Anyway, sounds like you do have the other stuff set up correctly, just dial it in on the water and it'll be fine. HTH.........ed

Re: ignition timing

thanks Ed, it does idle well and shift well so I guess that's where it's gonna stay for now, again thanks, that helps alot, J

Re: ignition timing

The trick is to get the idle as low as possible in gear, rather than a specific timing setting, to avoid beating up the gears when you shift. As the throttle is advanced, the timing starts to advance, then the throttles start to open (the primary pickup). Eventually, the timing reaches max advance and stops, but as you open up further, the throttles keep opening. Make sure that the max throttle stop (on the arm) happens before the carbs hit their own little stops, so that the arm takes the load of stopping the throttle cable and not the carbs.

Re: ignition timing

The actual numbers will vary depending on model, that said I have a book which covers a bunch of models - yours included. It's giving the following settings for your motor:
primary pickup/idle setting: 4-6 degrees BTDC
maximum advance setting: 21 degrees BTDC
idle rpm (in fwd gear): 550-650 rpm
full throttle 5000-5500 rpm

hope that helps.