low tension magneto question

[johnyrude200]

not to jump around but on that original motor posted about, I neglected to mention that the coil that is barely firing, I spliced a new connector onto it. I have seen in the past that with good coils, splicing basically makes the coil next to useless. Has anyone else noticed this?

However I also tried taking the bare wire lead from the coil and connecting it directly to the magneto lead (#1), coil still fired the same way. Switched magneto leads to the bottom coil and plenty of voltage coming from both magneto leads and firing strong on coil #2. So it’s coil #1 that is weak.

With the 2nd motor, the customer had the motor run totally fine and start right up easily on 3 occasions in a row, but at WOT after 2-3 mins, the motor dies out like it ran out of fuel and he can’t get it to restart no matter how many times he tries to pull it over. He lets it sit for 45 mins (or overnight), and it starts right back up like nothing ever happened. Fuel pump is working fine.

He said that at the end of last season he noticed a few times toward the end where it would not hit WOT or only do so for a few seconds then get stuck at mid-range. Carburetor is freshly rebuilt, float is set correctly. He has been running it this year and experiencing this, and I’m hesitant to say it is a plug issue because they are brand new plugs, but then again, the motor can’t be running anywhere near operating temperature in 40° water. Pumps water like a fire hose.

[fleetwin]

OK, well that sounds like the engine is dropping one cylinder…Probably can’t get it restarted due to the idle speed lockout….
Run the engine until it messes up for you, then do a spark test….
On the other engine, I have never noticed any problems splicing connections on coils, but definitely do NOT use butt connectors and tape…

[johnyrude200]

Well, I ran into an issue with this motor where the timing is 180° off. Used a timing light and confirmed it’s firing backwards. I will admit, I’m still trying to understand where/when to set the points using the timing fixture. I put the T (#1) pointer between the plate marks, and set the #1 points (port side of the motor) to open at this instance, and repeated for the other side, but doing this basically killed the ignition. By setting the points to open with the timing fixture lined up and when the protrusion on the cam makes the points opened, this reversed the firing pattern on the coils but I had a 1/2" bright blue spark on both sides (albeit backward firing). I know I’m missing something obvious. (and advanced thanks for whomever tells me what I’m missing).

That aside, I switched the ignition out completely for the CD version and it fired up on 2 pulls cold.

Now the reason why I wanted to mention this is that it’s a 1975 powerhead with good compression (105+ dry), and I just finished running it for 4 hours straight on my test boat in 37° weather…water isn’t much warmer. Once warm, this motor would not stall out with the throttle/timing retarded as far down as it would go (the low idle stop is completely removed).

So for what it’s worth, the internals of this unit is better than any newer powerhead I’ve used in my limited experience! Reminds me a of a 5.5hp last year that wouldn’t stall out without using the choke (triangle shaped nob).

I will say that I don’t think the thermostat opened once over this 4 hour period even after being run for 2 mins straight at WOT. Seems that when these cooling systems are completely correct, in colder weather/water, they pump so much water that they don’t even rise enough at the powerhead to activate the thermostats. Interested to see how things work in another 4 weeks when it’s 65° and the lake/river is 50-60° water.

[frankr]

I still haven’t totally figured out the timing fixture issue. It seems that at some point #1 and #2 were reversed. I haven’t found that documented anywhere. Bottom line, whichever worked is the way it is, at least on that particular motor.

[johnyrude200]

I am trying to understand from a conceptual standpoint how the system works. I get the 2 magnets with the N-S and S-N configuration, and that accounts for the ‘shared’ charge coil with the rest of the system similar to the universal magneto. So current is produced by the magnet passing the charge coil with both points closed, then a 1/3rd to 1/4 turn further (the gap between magnets) of the flywheel the timing cam opens the appropriate points and disperses this voltage to the respective top or bottom coil?

I mean, I could have easily just reversed the magneto leads to the respective coils and problems solved. But I refuse to send out a motor with my name/reputation that is set up wrong. It may ‘work,’ but at the end of the day somebody would see it and it would hurt my reputation down the road.

It was throwing a 1/2" spark on both cylinders using the timing fixture, and by looking at the timing cam protrusion this did not correspond to where the stator plate index would open up the actual points. It made no sense on Friday (just got back to it earlier today). When I saw the timing was OFF by 180° using the timing light (and when it would only spit randomly using the electric start when I threw it into the barrel…knew immediately it was backwards), I followed the directions I had for the fixtures and that made it so all I had was a 1/32 spark on cylinder #1 and nothing on cylinder #2.

After building this unit from scratch from 10-12 donors, I said the heck with it, spent 20 minutes, and installed CD ignition.

But regardless, I need to know what I’m missing here so I can work on these motors as there are a heckuva lot of 1974-76 OMC’s that pass through my doors so it isn’t something I am going to avoid due to lack of knowledge.

[fleetwin]

Well, I probably need to reread your latest posts….But, please know the engine will not run at all with the timing out 180 degrees, the most you will get is a spit or backfire. So, if the engine was running, the timing surely was not out by 180 degrees. Timing light/tach pick ups can be pretty sensitive, and they will often pick up inputs from a lead they are near/next too, even without being actually connected to them…
OK, so you have converted this engine to CD ignition….But, you mention the engine will not stall out, even with the throttle completely retarded and the idle stop removed. This concerns me a bit. You have swapped a lot of pieces, it is possible that the various linkages are not actually retarding the timing enough for idle speeds. What is more concerning to me is that the various linkages you are using might be over-advancing the timing at WOT, which could lead to big trouble. Unfortunately, the flywheels are not gridded on these engines, and there are not specs for WOT timing. Just something to think about when making swaps like this.

[johnyrude200]

The RPMs are OK at the top end, and if I really hold the thing as low as possible it will eventually stall out, but it revs down exceptionally low (probably into the 400RPM range).

The question I had was before I swapped out the ignition from being low-tension magneto to CD. With the CD, it works fine. With the low tension, it was firing backwards. Trying to figure out what I missed.

[RICHARD A. WHITE]

Could you have possibly connected the wrong points to the wrong coil???? Thinking out loud….and it hurts..LOL

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

[johnyrude200]

blue white lead goes to top, blue lead goes to bottom. Didn’t miss that one 🙂

[RICHARD A. WHITE]

I was referring to the older mag….not the CDi…lol

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

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