How Important is OMC Ignition Timing?

[billy-j]

fleetwin wrote. There are two "timing marks" on the mag plate, one mark is used for "new points", the other is used for an existing set of points, there are two marks on the flywheel as well, one for each set of points. The extra timing mark is used for new points to account for initial rubbing block wear. Sometimes it is recommended to set new points at .022" for this same reason. My question is ? Are these the two parallel marks on the breaker plate ? I have never read anywhere that these two marks are for new and used points. If so would the first mark you come up to be the one for new points. Let me know what is correct. Bill,

[chris-p]

Yes this is for setting the points with a timing fixture. The two vertical, parallel hash lines on the mag plate.

What fleetwin wrote is in the service manuals actually.

If I install new points, I set them to break at the first mark as stated. If I cleaned/dressed the old points, I set them to open in between the hash marks.

[RICHARD A. WHITE]

So, if points are set to open exactly 180 apart, I understand how that helps. does the points cam and or cam lobe automatically set the opening to .02?

Here is why I ask, If I set the points to open 180 apart, then rotate just past that point and then set them to .02, I will in effect, possibly change the location of them opening.
I am thinking the lift of the cam will get the .02 needed….correct?

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[legendre]

quote Richard A. White:

So, if points are set to open exactly 180 apart, I understand how that helps. does the points cam and or cam lobe automatically set the opening to .02?

Here is why I ask, If I set the points to open 180 apart, then rotate just past that point and then set them to .02, I will in effect, possibly change the location of them opening.
I am thinking the lift of the cam will get the .02 needed….correct?

If the points are just beginning to break open at the position indicated by the timing tool / mag plate relationship, they will measure 0.020" – within reasonable tolerance – when fully open. The idea being, that by design (and careful manufacturing) the crest of the points cam is approximately 0.020" higher than the correct "fire" point at the base of the rising slope. It may in fact be that the crest of the cam is (almost) exactly 0.020" taller than the base circle (aka 0.020" total lift) but I can’t say that’s the case – easy enough to measure, though.

While the actual points gap is reasonably important, as it effects the dwell time and hence ignition efficiency, having the two cylinders firing exactly 180′ off and at the correct time is ultimately more important to running quality.

Or that’s as I understand it.

[chris-p]

020 is a reference the factory can give to the average Joe, without a Timing Fixture/Buzz Box combo to set their ignition. They can say, when the hole in the flywheel is over the points, set it at 020, or when the rub block is at the highest point on the cam, usually the crank keyway, set them at 020.

That does get you pretty darn close usually. Although, it doesn’t get them to fire exactly 180 degrees apart. Unless you are Spider Man!

Using the timing fixture, and buzz box (or multi meter, test light) will. Which in turn, gives the improved idle.

Richard, I am more experienced in OMCS. I believe, you could be referencing Mercs, which I know diddly about, so not sure how it applies.

[RICHARD A. WHITE]

quote wbeaton:

I set up hundreds of motors without the timing tool and they all worked just fine. Then one day I tried a timing tool and I Was sold. It was faster and provided a perfect spark. I would never went back to the feeler gauge. I use a buzz box instead of a multimeter. It works much better and you don’t have to remove the wires to the points.

I obviously fail because every time with wires connected, I get continuity. So please explain with pictures preferably exactly WHERE you place the black and red probes. I can get it to work but I have had to remove ALL wires from the points to get it. Pictures even on just one set of points will do.

Thanks

Richard

http://www.richardsoutboardtools.com
classicomctools@gmail.com

[Mumbles]

You don’t have to remove any of the wires if you are using a timing tool and a digital ohm meter.

With the points closed, you will have a very low ohm reading but when the points open, the reading will increase slightly because it is reading the primary winding in the coil now. I think the pressure of a screwdriver hooking up the leads again can bend the points slightly changing the gap.

[legendre]

quote Mumbles:

With the points closed, you will have a very low ohm reading but when the points open, the reading will increase slightly because it is reading the primary winding in the coil now.

This is the issue, and it’s why you can’t use a light or buzz-box – neither can really tell the difference between 0 and 1 ohms. When the points are closed, the ideal reading is ZERO (0) ohms – it won’t be zero, but dang well close. When they open, the reading will rise to the value of the primary winding, which is around 1R (one ohm) or even less. This is too small of a change to be obvious on many meters, even digital models.. you need to pay close attention.

Removing the coil primary wire from the points will fix this, as you should be able to leave the other two wires (kill-switch and condenser) connected without issue. In that case, readings will go from ‘zero’ to nearly ‘infinite’ when the points break open.

[legendre]

quote Richard A. White:

I obviously fail because every time with wires connected, I get continuity. So please explain with pictures preferably exactly WHERE you place the black and red probes.

I have no reason to believe you’re putting the probes on the wrong measurement points. The problem is (as stated in my previous post) is the definition of ‘continuity’.

If you’re using a continuity light or buzz-box, there’s no discernible difference between 0 and 1 (zero and one) ohms – either state will illuminate the lamp or buzz the box. Problem is, it’s this roughly one-ohm shift that delineates the open vs. closed points condition.

So you either need a more sensitive instrument, you must pay closer attention to your current instrument (DVM) or you must remove the coil primary wire from the points connection.

[RICHARD A. WHITE]

Ok,. I get that… the light is getting a bit brighter…. but you say, and understand I am no flipping genius, you can’t use a light or a buzz box. I flipped my Digital M/M to make noise when the points are closed and with the leads touched the non moving side of the points, and grounded to the base. I guess that is still reading ohms correct?
It just makes noise until the points break, so my question is, how far apart do the points get before it will stop buzzing?

This question has got my interest piqued as I do understand the "lift" of the cam will get me the .02 but by making sure both sets of points open 180 degrees apart will allow motor to run so much better, than just looking for them to open then setting the points to .02 gap

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classicomctools@gmail.com

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