Timing a 1975 115 merc at full throttle !!!???

Joined
Jun 22, 2014
Messages
12
Do I have to time my engine at fu throttle ? If so what degree ? And how ? Any good info or vids or instructions would be helpful thanx
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,108
Greg, Remove all spark plugs but the top one. Install them into their plug wires and ground them to the block. Now set the throttle to full and crank the motor, timing light on top spark plug wire and observe the reading. Set max spark advance to 21* BTDC. Idle timing pickup on that distributor ignition motor is 4-6* BTDC.
 
Joined
Jun 22, 2014
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12
Hi Chris I went to time my motor yesterday and did what you had said the only problem is I have a neutral safety switch that won't let me roll it over, anyway to bypass it ??
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,108
Sure, but first I would remove the prop for safety. Jumper from the red battery cable on the starter solenoid to the small post with the yellow wire on the starter solenoid. That will activate the starter solenoid and crank the motor.
 
Joined
Jun 22, 2014
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12
Seemed to work great ! Now just to wait until the weekend to try it out, I timed it about two degrees on the retarded side of stock ( I was told to do this because of the new fuel )
 

wired247

Lieutenant Commander
Joined
Oct 8, 2011
Messages
1,557
You'll be fine at 21 degrees with that motor. Disconnect the carbs from the linkage and start the motor. Open the throttle control all the way . You'll only get 1500-2000 or so RPM with the carburetor throttle plates fully closed and the timing fully advanced but the timing WILL be fully advanced. Best to check TDC on each cylinder and use the highest reading cylinder to set the timing off of.

You can go up to 23 degrees and get better off idle and mid range if you use premium gas. I dont know about where you are at but thats all they serve on the water here so its worth setting the motor up to take advantage of it.
 
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