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My motor won't kill

S

sdraves102

Member
I have an old 1955 Johnson 25 Hp outboard that I recently converted to a fuel pump instead of a pressure tank. Pumped the ball hit the starter
and off she went an went and went. I shorted the top of the cutoff switch to ground and it kept on going. I had to pull the choke lever choke it off.
Any ideas? Am I just not understanding how the cutoff works?
 
There should be two black wires connected to the ignition points (1ea wire to 1ea point). These two wire should be hanging down from the armature plate under the flywheel, one of which is no doubt attached to the vacuum cutoff switch.

The other wire should lead to one of the terminals of a two terminal push button or one of the "M" terminals of an ignition switch that has two "M" terminals.... then a wire would lead from the remaining terminal of the button or "M" terminal of the ignition switch back to the vacuum cutoff switch.

When the button is "open" (or key ON) there is spark.... when the button is pushed in (or key OFF), that shorts the points out and there is no spark (the engine stops running).

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

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fdrgator said:
1955 25hp never did have a stop switch, nor the wires to hook one up. You choke it to stop it.
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My previous reply was assuming that in the years since the engine's manufacture, someone had installed the stop circuit but that it was disconnected, cut, partial loss, whatever. Actually the engine had no idle stop to speak of and it was made to stop simply by retarding the throttle to an extreme.
 
joereeves said:
My previous reply was assuming that in the years since the engine's manufacture, someone had installed the stop circuit but that it was disconnected, cut, partial loss, whatever. Actually the engine had no idle stop to speak of and it was made to stop simply by retarding the throttle to an extreme.
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the motor has one coated wire coming off the magnito to the top screw of a normal looking seahorse style cutoff switch. I ran one m key switch
contactors (black wire) to the the top of the magnito screw also the other m contact to engine ground thinking I was grounding out the points.
Am I wrong?
 
Joe, I realize what your were thinking and do not find fault with it. I believe the next year did have an idle stop and the printed instructions were to choke it to stop it. sdraves, your motor is as-built, just one wire, not made for a kill switch. Your hookup will kill one cylinder, but the other one will continue to run, as long as it is running correctly and the throttle is set high enough. As Joe said, you probably can kill it simply by retarding the throttle. If you really care, you can add a wire to the other set of points and then you can use a kill switch. That feature started in 1958.
 
kimcrwbr1 said:
You can add the other wire to the set of points you will need to pull the flywheel. When you choke it it makes it a little difficult to restart right away it is a good upgrade. If you pull the flywheel look close at the coils if they are cracked you need new ones anyway and put new points and condensers in also. The cutout switch only turns of one set of points and as you know these motors run pretty good on one cylinder it just wont rev very high. Allways disconnect the battery when connecting the kill wires to the ignition it takes a split second to fry the coils if shorted to battery posative. your just shorting both points together to kill the motor and it will start right up with a quick click of the ignition switch. You have to pull the armature plate to replace the coils take a pic of it first before you take it apart so you know how it goes back together you must push the wires all the way into the coils and push the boots on before you install them into the plate. Look close how the coils are lined up with the bosses before you take it apart and make sure they are put back the same for clearance/gap for the flywheel magnets. If the coils are dark colored just replace them they will fail on you and check the plate for any wobble up and down if so get new mounting parts the bracket and ring that holds the plate down. If adding the kill wires make sure they do not restrickt movement of the armature plate or rub on anything. Those are good old motors and with a little TLC you should get plenty of good service out of it you are mixing 24:1 correct?
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I used a tank of 50:1 I had for my 40 hp didn't think it would hurt for the test start. Good to know 24:to 1. If I get this worked out could you give me a little advice on adjusting the high speed Ideal.
 
You can't do it unless it is on a boat, on the lake, in gear, and running full throttle. Before you begin, get it somewhere in the neighborhood at 3/4 turn open from lightly seated. Then at full throttle turn it slowly clockwise until it starts to falter, then turn back to the left (counter-clockwise) till it regains power. Then do the same with the slow speed, beginning at one and a half turns. Running at slow idle, turn clockwise till it falters or sneezes, then back to the left till it idles smoothly. Fine tune at high and slow speed, tweaking it a bit if necessary. Now, wasn't that easy?
 
Sorry it took so long to reply had to go to Ohio on business for a week. This is all great advise. But let me see if I understand the wiring issue. To me it looks like
I have to short the two NON grounded sides of the points to each other when the key is in the off position to stop the motor. I originally thought I needed to tie the
the the two non grounded sides of the points together and hook it to one side of the key switch,then hook other side of the key switch to ground and short both to ground with the switch in the off position. but that would fire both pistons at the same time. Is my thinking right or an I still off base?
 
To rig up a kill switch: Two black wires (one from each set of points) lead to the kill switch. One wire is already in the magneto, you will have to add the other one. The switch does absolutely nothing till you turn it off. But when you do turn it off, it makes an electrical connection between the two black wires. That shorts the two sets of points together, and prevents them from working. If you want the electrical explaination for that, consider this: One set of points opens at the correct time to fire its associated cylinder. The other set of points is closed at that time (grounded). So, the set that just opened can't do anything because it is connected via the kill switch to the closed set (grounded). In effect, both are grounded at all times when the switch is off.
 
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