mercury 7 1/2 hp

[seakaye12]

quote outbdnut2:

I’m curious: Does anyone have a circuit for one of these stators?
Dave

Good question. If such a schematic is out there….it is a very well kept secret. And; why?

If anyone knows of a source…..please share.

[guzzi-john]

Obvious trouble w 70/71 or they wouldn’t have changed design. As I’m not an OB guy how problematic are the CDI systems in general? I’m now leaning back to the Chryslers to augment my existing Sea King 6. Have lines on 2- a 6 & 10 Chizler.

[outbdnut2]

quote guzzi john:

As I’m not an OB guy how problematic are the CDI systems in general?

If CDI’s are designed right, they tend to run forever. They have been used in cars for many years now. Most outboard CDIs do not have mechanical Maker points and that’s a plus. In the early days of the three cylinder Johnsons and Evinrudes, I heard of a lot of those CDIs dying and even towed a few off the lake I’m on. One guy I towed had just had his 4th one die in two years. I have to believe OMC corrected whatever that problem was long ago.

In the 1970s, I used to repair aftermarket car CDIs – specifically the Delta Mark 10s – good circuit, but they had some quality problems with a couple of parts and had corrosion problems with moisture getting into the non-sealed box – Once I managed to discuss those issues with their circuit designer on the phone.
Dave

[jeff-register]

Dave,
I have never found drawings on much in service manuals. Bet the scr was rated @ 70% or less. It is the main electronic switching solid state device. A few guys at Johns old merc have reverse engineered many switchboxes. When smoke tested the scr fails, then control ckts.

[guzzi-john]

Ok, even if the thing sparks when cranked I assume when running and revved the high speed coils could be dead(just cranking uses low ones right?) or the CDI simply poops out when warm. Not simply good or bad.

[20mercman]

quote guzzi john:

Ok, even if the thing sparks when cranked I assume when running and revved the high speed coils could be dead(just cranking uses low ones right?) or the CDI simply poops out when warm. Not simply good or bad.

I wouldn’t get too concerned over the function of the CDI units. As I stated, the usual issue is bad insulators on the leads from the points. Otherwise, try it out and see. As I have said, I would not hesitate to own one of these motors. I do own two of the 1972 20hp motors.

Steve

[outbdnut2]

Something I’ve noticed on CDI ignitions. Because the voltage is high, but very short duration compared to conventional ignitions, the spark can be hard to see in a spark plug gap – even opened to 1/4 inch, especially if you are in bright light or sunlight. On some, I’ve had to close the garage door and shut off the lights -them pull the motor over to see the spark.
Dave

[guzzi-john]

Am I assuming right that there are 2 separate signal coils feeding the ignition coil for each cylinder? And if that’s the case is there malso a mechanical advance or is that taken care of by the HS coil’s position? Also you infer that if I have a strong spark when cranked all should be well save for those grounding issues? I’m sorry for so many questions but manuals from library aren’t here yet.

[20mercman]

The magneto rotates on the crankcase via the throttle linkage to provide the timing advance and to open the throttle on the carburetor.

[guzzi-john]

Ok why the 4 coils in a row?

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