OMC 115 Timing

[carpenterken]

The timing on my 1975 115 says to set it at 24 deg btdc.. I checked it today and, it was only 6 deg. btdc
I looked and looked and could not figure out how to reset it.
Can any one tell me where the adjustment is for timing?
Thanks.
Ken.

 

[Joe Reeves]

Re: OMC 115 Timing

Standing in back of the engine, facing it, which spark plug did you have the timing light connected to?

And did you have the timer base pushed completely up against the full spark advance stop screw?

Spark plugs removed, engine NOT RUNNING but in forward gear, throttle set to full throttle/full spark advance.

(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 temperture.

The full spark advance can be adjusted without have the engine running at near full throttle 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 a spark tester and have the 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.

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?.

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.

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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[carpenterken]

Re: OMC 115 Timing

the timing light was on the top right plug wire. The # 1 coil.
24 deg is what it says on the block sticker.
It was at 6 deg at idle speed running.
Thank You.

 

[Joe Reeves]

Re: OMC 115 Timing

The 24? (if that's what the full spark advance setting is supposed to be), would be the setting/reading in gear, and at full throttle, full spark advance, not at idle as at the idle setting the timer base (spark advance) is at its lowest setting under the flywheel.

The information I inserted above will let you check the timing.