To kill a 40 horse !

[Uxboat]

A gentleman gave me a 1961 Johnson 40 outboard,which runs great after replacing all the hose,s and test running it on stand with the lower end in a garbage can of water I did not know how to to shut it down proper.So I choked it to death,I did get a Johnson cdrom but it does not go back far enough so my question is what is the right way ? If you stand facing the prop on the the right side there is a black wire that disappears under the flywheel,thinking that it might need to be grounded to stop it.

I also was wondering if anyone knew what the electric / vacuum device on the left section was ? Sorry no pictures but I am not sure how to post it.

Thanks Mike

 

[bktheking]

Re: To kill a 40 horse !

The vacuum device is a high speed cut out switch to prevent over revving. If this is an electric start, there should be 2 black wires coming out of a wiring harness, if you touch them together while the engine is running the motor will shut off.

 

[samo_ott]

Re: To kill a 40 horse !

Manual's also have the 2 black wires coming out from under the flywheel. As mentioned, short them together on a switch and it will stop. That's the way it's supposed to be done. The ignition switch does it for you.

 

[Uxboat]

Re: To kill a 40 horse !

I only see a single black wire coming down from underneath the flywheel,it has a starter motor and a short ground lead on the cylinder head going nowhere.I am thinking there was a ignition switch in the boat and the short ground wire on the head connect via the ignition switch to the black lead to shut the engine off.Does this sound right?

I also was told on these older motors there was no charging avaiible for the battery,you had to remove the battery from time to time and charge it.This should be a easy project:

new ignition switch and battery to power up a solenoid to engage the starter
a simple switch to connect the black wire to engine ground to kill the ignition

Sound about right ?

Cheers Mike

 

[Willyclay]

Re: To kill a 40 horse !

If you are interested in some service information on your motor, send me a Private Message with your email address. I scanned and saved a non-factory service manual that covers all 30-40HP motors built by OMC from 1956-1964. A belt-driven generator was an option for that motor. Another forum member told me he was installing an alternator on his 40. I'll see if he will post something about that mod in this thread. Good luck!

 

[bktheking]

Re: To kill a 40 horse !

You should have a wiring harness coming out from the motor then if it's electric start. There should be 2 black wires in the harness, they go back to each coil/point side of the magneto. If you connect one of wires to ground it will only cut spark to that side of magneto, I've been through this before. The easiest way is to connect the 2 black wires to a momentary switch, when you want to stop the motor you push the button. There was a generator belt driven charging system back then but it was rare on most motors and expensive today to find one.


I will post the wiring diagram for your motor in a sec. The ignition switch if it's got 2 M wires can go to each one of the black wires.

 

[lindy46]

Re: To kill a 40 horse !

The vacuum device is a high speed cut out switch to prevent over revving. If this is an electric start, there should be 2 black wires coming out of a wiring harness, if you touch them together while the engine is running the motor will shut off.

That vacuum cut-out switch should have a wire going to the points under the flywheel which spark the lower cylinder. The other black wire goes to the other set of points and then on up to the ignition switch ("M" terminal). A jumper wire from that same vacuum switch wire should go to the other side of the ignition switch (other "M" terminal). When the switch is shut off, it closes the connection between the "M" terminals, grounds out the points and the motor stops.

 

[F_R]

Re: To kill a 40 horse !

There are two black wires coming from below the mag plate. At least there are supposed to be two. If somebody has removed one of them, what can I say? One goes directly to one of the M terminals on the ignition switch. The other one goes to the center terminal on the vacuum cut-out switch. Another black wire goes from that same center terminal to the other M terminal on the ignition switch. When you turn the key to "off" it electrically connects the two M terminals together, stopping the motor.

The vacuum cut-out switch won't work as intended unless it is also connected by a wire from the corner of it to a mercury switch on the throttle gear.

The wire coming from the cylinder head is the sensor for the overheat warning light.

 

[bktheking]

Re: To kill a 40 horse !

So that's what MS means in the diagram, mercury switch, F R you are the man. What does the merc switch do, if you're out with the boys and attempt a james bond 360 off of a ski ramp was it supposed to cut the engine in flight On a serious note, what does it do for real? I guess if the throttle is pushed too far forward it caused a mercury bulb to make contact and short? I look at my buddies 40 and it had a vacuum tube going to the port on the engine, I'm guess this is what opened the vacuum switch?

 

[samo_ott]

Re: To kill a 40 horse !

Yes, the mercury switch prevents the starter from starting if the throttle is set to high to start it.

Oh and yes, there is no charging circuit in the engine. I have a one foot square solar panel on my boat for my '62 25hp and it keeps the battery topped up fine. I never had to charge the battery once all summer.

 

[bktheking]

Re: To kill a 40 horse !

So, as FR mentioned without the merc switch this "vacuum switch" won't work? Our 40 is wired to a newer evinrude control set without the merc swich, so it's safe to say the vacuum swith is useless then?

 

[lindy46]

Re: To kill a 40 horse !

On a serious note, what does it do for real? I guess if the throttle is pushed too far forward it caused a mercury bulb to make contact and short?

It just keeps the starter from firing if the throttle is advanced too far. Works through the starter solenoid.

 

[lindy46]

Re: To kill a 40 horse !

So, as FR mentioned without the merc switch this "vacuum switch" won't work? Our 40 is wired to a newer evinrude control set without the merc swich, so it's safe to say the vacuum swith is useless then?

Mercury switch has no connection to the vacuum cut-out.

 

[bktheking]

Re: To kill a 40 horse !

I guess all that safety crap is bypassed on ours, no wire to the solenoid on our 40 or merc switch.

 

[samo_ott]

Re: To kill a 40 horse !

So, as FR mentioned without the merc switch this "vacuum switch" won't work? Our 40 is wired to a newer evinrude control set without the merc swich, so it's safe to say the vacuum swith is useless then?

The vacuum switch is independent of the mercury switch. The vacuum switch grounds out one coil in the event of a runaway condition (high vacuum) and thus stops one plug from firing thus slowing the engine down.

 

[Uxboat]

Re: To kill a 40 horse !

Okay so that makes sense,there is a second black wire running around past the carb to the vacuum switch.So all I need to do is ground the black wire on the fuel pump side.The solar panel sounds good too,I,d looked into early on.Hard to believe how well it starts and runs considering the age and amount of service it has likely seen

Thanks everyone for pitching in with advice and scans. Cheers Mike

 

[F_R]

Re: To kill a 40 horse !

Okay so that makes sense,there is a second black wire running around past the carb to the vacuum switch.So all I need to do is ground the black wire on the fuel pump side.The solar panel sounds good too,I,d looked into early on.Hard to believe how well it starts and runs considering the age and amount of service it has likely seen

Thanks everyone for pitching in with advice and scans. Cheers Mike

Fer cryin' out loud, already, the 35 and 40hp motors from 1958 thru 1961 have a DUAL mercury switch!!!!

One section prevents starting the motor (electrically) at high throttle settings.

The other section enables the vacuum cut-out switch at low throttle settings only, because if enabled at certain throttle settings it can cause a high speed miss. How does it enable it? The vacuum cut-out seitch is mounted on a plastic plate and therefor is not grounded. The mercury switch grounds the body of the vacuum cut-out switch only when at "slow" throttle. It can't work if not grounded.

What does the vacuum cut-out switch do anyway?? It prevents runaway if for some reason you rev it up past idle speed in neutral. Without a functional cut-out switch, runaway will occur and you can't slow it back down--it just keeps revving.

Here is a "real" diagram
http://i155.photobucket.com/albums/s311/frankr_photos/Wiring1958_6135_40hpwithoutgenerato.jpg