GT 150 firing order

Duck Loads

Petty Officer 3rd Class
Joined
Apr 15, 2003
Messages
86
I have been studying the factory service manual for my J150stlcem to check the sync & link. ('89 Johnson GT150)I cannot find the firing order or even what cylinder is no. 1.<br /><br />Is the no. 1 cylinder top starboard?<br />Are the starboard cylinders 1, 3, & 5 and the ports cylinders 2, 4, & 6 top to bottom?<br /><br />I don't have a test wheel to set the WOT timing per the book. What timing error (if any) should I expect to see if I check it at WOT cranking speed with the plugs removed?<br /><br />Thanks a bunch,<br /><br />Duck L.
 

Joe Reeves

Supreme Mariner
Joined
Feb 24, 2002
Messages
13,262
Re: GT 150 firing order

Duck.... You are correct ie Starboard cyls top to bottom are 1,3,5. Port cyls top to bottom are 2,4,6.<br /><br />The firing order is simply 1,2,3,4,5,6.<br /><br />I don't know what the full spark advance setting is for that engine. Hopfully someone will jump in here with that information.<br /><br />However, to check the timing at cranking speed, it can be accomplished as follows:<br /><br />(Timing At Cranking Speed 4°)<br /><br />The full spark advance can be adjusted without have the engine running at near full throttle as follows. <br /><br />To set the timing on that engine, have the s/plugs out, and have the throttle at full, set that timer base under the flywheel tight against the rubber stop on the end of the full spark timer advance stop screw (wire it against that stop if necessary). <br /><br />Rig a spark tester and have the spark gap set to 7/16". Hook up the timing light to the #1 plug wire. Crank the engine over and set the spark advance to 4° less than what the engine calls for. <br /><br />I don't know the full spark advance setting your engine calls for, but to pick a figure, say your engine calls for 28°, set the timing at 24°. The reasoning for the 4° difference is that when the engine is actually running, due to the nature of the solid state ignition componets, the engine gains the extra 4°. <br /><br />If you set the engine to its true setting at cranking speed, when running it will advance beyond its limit by 4° which will set up pre-ignition causing guaranteed piston damage! You don't want that to take place. <br /><br />No need to be concerned about the idle timing as that will take care of itself. The main concern is the full advance setting. <br /><br />Be sure to use your own engines spark advance settings, not the one I picked out of the air here in my notes.
 
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