Evenrude 35 Hp model 25930 1957 Mercury switch wiring question

I have a wire that hangs close to my mercury switch which appears to have been attached to the mercury switch at the starboard side of the engine behind the starter motor and down low on the block. There is another larger guage wire still attached to the mercury switch. The motor runs without it attached but it bothers me not knowing. Also what is the mercury switches function. The new replacement switch comes with one wire but no apparent place to attach a second see the pic of part # 376867 at least what I can see in the pic. I do not have the switch in hand.
Thanks for the help.

fdrgator said:

The switch function varies slightly from year to year. In the case of a 1957, it prevents starting (if electric start) at fast throttle settings. It also prevents operation of the vacuum cut-out switch at fast throttle settings, both on electric start and rope start models.

EDIT: A ground wire was added in later production. Early production relied on grounding through the rotating throttle gear/shaft (not very reliable).

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Thanks fdrgator. Is it safe to say that the very thin black wire that looks like it might attach to the mercury switch is the ground you speak of. The other larger black wire is well attached but I have not traced it.

So the Merc switch cuts the vacuum switch out of the loop when the engine is running at high and full throttle. I thought the vac switch was to keep the motor from over reeving which I would think possible even in gear and running across the water.

It is a serious honor to have a resource like you to shed light on these problems. thanks for you time and Knowledge.

Thanks for the great information. I appreciate the depth or you knowledge.
I am still not sure where the thin wire that is right next to the mercury switch on my 35hp. It is hanging so close that I believe it must attach. There is another wire that is still attached to the switch. Is this thin wire the one that goes to the cut off switch or to ground or does it attach some where else close by. Is there a way to test this system Ie the mercury switch and the cut off switch.

thanks again for the diagram and the help

fdrgator said:

The wire that is welded to the little post on the mercury switch goes to the outside corner of the vacuum cut-out switch.

There should also be a separate wire whose terminal goes under the screw that mounts the mercury switch. The other end of this wire goes to any good ground, preferably at the engine block.

I haven't looked up your model number. Save me the effort---is it electric start or just rope start?

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Model 25930. Electric start. The solanoid is stuck after not using the motor for about 12 years. I was able to start and Run briefly after cleaning the carb. Is there any fix for the solinoid or should I just buy a new one. I will be back to the boat next weekend and will shoot some picks for your perusal. Would like to know if the solinoid could be in stuck. Thanks for the help

I am pretty sure the safety switch is strictly for the ground to the start solenoid and the cutout switch is always connected. If you lose a prop or the engine kicks up from a deadhead while motoring WOT it will cut out the bottom cylinder to avoid a run away engine. My 58 super sea horse 35hp had a dual mercury switch but that was over 20 years ago but cant remember how it worked but believe it was a tilt safety switch as well but not sure.

kimcrwbr1 said:

I am pretty sure the safety switch is strictly for the ground to the start solenoid and the cutout switch is always connected. If you lose a prop or the engine kicks up from a deadhead while motoring WOT it will cut out the bottom cylinder to avoid a run away engine. My 58 super sea horse 35hp had a dual mercury switch but that was over 20 years ago but cant remember how it worked but believe it was a tilt safety switch as well but not sure.

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See the wiring diagram, post #2. The cutout switch is grounded by the mercury switch at slow throttle settings only. That prevents possible misfiring at cruise throttle settings.

Henry, it would be rather unusual for the solenoid to stick. But if you are sure it is, might as well replace it.

It looks like I can test it by taking power form the batter pos side of the solenoid and energizing the battery side terminal which will then flow to the Kill vac switch and the solonoid should engage. so far I have not had a voltage meter to check for current on the terminals so I was working in the dark. I will be with the boat this weekend and will give it a try and see if it is a bad wire to the solenoid or a bad solenoid or bad starter button.
I sure appreciate your help. If stuck can they be loosened and gotten to work again in your experience.