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I'm bringing a 1983 35hp out of retirement that has had it's WOT timing set by the starter motor, now I'm seeing posts online stating OMC put out a bulletin in the past stating to subtract 4 degrees from the manuals setting. Is this just meant to safely run the motor until it can be tested live on water?
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If your comment of "Timing set by the starter motor" means that the timing was set by my method of setting the full advance timing at cranking speed..... subtracting the 4 degrees from the normal full spark advance setting is due to the electronics.Originally posted by mphelle View Post
If the normal full advance timing was (to simply pick a number) 20, the timing at cranking speed should be set to 4 degrees less, to 16. The reason for this is that when the engine is actually running, the electronics within the powerpack automatically advances the timing another 4 degrees to be at the specification setting of 20.
If one set the timing to the actual factory specified 20 degrees (ficticious example) at cranking speed, when running, the electronics would advance it to another 4 degrees 24 (too high) which would result in pre-ignition, melted pistons, powerhead failure.
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(Timing At Cranking Speed 4°)
(J. Reeves)
NOTE: If your engine has the "Fast Start" feature", you must disconnect/eliminate that feature in order to use the following method. The "Fast Start" automatically advances the spark electronically when the engine first starts, dropping it to normal when the engine reaches a certain temperature.
The full spark advance can be adjusted at cranking speed,"without" have the engine running as follows.
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).
Rig up a spark tester on the #1 cylinder plug wire. 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.
It's a good idea to ground the other plug wires to avoid sparks that could ignite fuel that may shoot out of the plug holes. I've personally never grounded them out and have never encountered a problem but it could happen.
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 components, the engine gains the extra 4°.
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.
No need to be concerned about the idle timing as that will take care of itself. The main concern is the full advance setting.
A fellow member from one of the various marine forums suggested having water supplied to the water pump (flushette or barrel) simply to provide lubrication to impeller. A worthwhile suggestion I thought, and entered here.
Be sure to use your own engines spark advance settings, not the one I picked out of the air here in my notes. -
Thanks for your reply and I'm glad I checked before running it. I'll set it with your instructions and then check it again on the water when the weather warms up.
Do you have any insight into OMC's investigation of motors being damaged by using the starter timing method which led to the -4 bulletin? Were techs using it as a time saver or owners trying to save money?Comment
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Thank you for responding, I'm retired and enjoy reading information about the good old days when there was competition among manufacturers, and when they responded to customer input to protect their reputation.Comment
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