1955 evinrude 25hp ignition switch

[cbouchard]

i have tried to connect a regular ignition switch on subject motor. The switch has two “m” post on it..I understand that if I connect a wire from each set of points (on the same lug that the condenser attaches to) to each of the “m” lugs on the switch it will shut the engine down. I guess what is supposed to happen is a complete loop is created between each set of points which grounds out the ignition and shuts it down BUT it doesn’t. I have to choke it to shut it off. I was wondering if I could put both wires coming from the points and attach them to one of the “m” post on the switch and on the other “m” post run a wire directly to ground. Then when I put the switch to off the loop will be from the points to ground directly. Will this work without ruining anything within the electrical system like coils or condenser. Thanks, cliff

 

[cbouchard]

Just thought of something else relative to my post..how will the vacuums switch be effected. I.e if it kicks in it is supposed to short out the ignition to the lower cylinder stopping the run away situation while keeping the engine going on number 1. If I somehow connect both sets of points at one m terminal will the vacuum switch kill the engine by shorting out both cylinders??

 

[RCO]

No, the engine will not run with both points wires touching. Either your switch is bad, or something is amiss in the two black wires from the magneto .

 

[F_R]

Confirming, a wire from each set of points to each M terminal is correct.
What is the model of your 25? Early ones were not wired for a switch, but of course it can be modified.

EDIT: Oops, I see you said it is a 1955. Can be modified for a switch

 

[cbouchard]

I will do some continuity test and see what happens..thanks.

 

[Papa gone fishing]

I just did a ignition switch on a 1961 18HP that should be similar to your 55.
I used the recommended OMC switch part # 508180.
Here is the link and I hope it helps you. Dane.

 

[cbouchard]

Thanks everyone for your help. Did some testing...switch is fine when in off position there is a loop between the m posts..tested leads going to each set of points and again individual leads are good..meaning when I put the ohm meter on each end it tests positive for continuity. Motor still does not shut off. Maybe I am testing incorrectly??

 

[F_R]

There is something wrong with those leads going to the points or they aren't really going to the points. Put your ohm meter probes on the two leads at the switch end (disconnected from switch)

 

[cbouchard]

I think I did that but will try it again. Just so that I am 100% sure...when I put the ohm meter on each of the leads coming from the individual set of points I should get a complete continuous circut no matter which points are open or closed.. and because one is always closed it is a grounded circuit.which is why the engine shuts down..is this correct???

 

[cbouchard]

Just thought I would post a couple of pictures of the motor

 

[F_R]

Your basic understanding is correct. Just in case, the wire routing is as follows:

Wire from one "M" switch goes directly to one set of breaker points.

Wire from other "M" switch terminal goes to the vacuum cut-out switch. Another wire continues from vacuum cut-out switch to the other set of points.

The points are not the actual kill circuit, although they do function as a secondary route. The two coil primary windings are the first route. Circuit is one of the coil's ground, through primary winding, to points/condenser junction, to ignition switch "M", across switch contacts when "off" to other "M", and back to other points/condenser junction, to and through other coil primary winding, and back to ground, completing the loop. The vacuum switch merely taps into one of the wires along the way.

Simple if you understand basic electrical circuits, and I think you do.

 

[cbouchard]

IT WORKS!!!!!!don’t know what o did different but it works now. Thanks everyone for your support. Now to get the merc 300 going. Cliff