'71 merc 135hp won't shut off!!??

hi folks, started right up after a long winter. that's the good news. bad news is it won't shut down with the key! had to disconnect the fuel line & choke the hell out of it to stall it out. maybe it's the key switch, i don't know, but i don't want to spend anything to fix it. i'm just wonderin if there is a quicker simpler way to shut her down when i want to stop and fish? or does someone have an idea of what else i could check myself to get the key to work? thanks as always for any help,
art

Re: '71 merc 135hp won't shut off!!??

anyone?

Re: '71 merc 135hp won't shut off!!??

The white wire going to the CDI ign box (note NOT the white wire coming out of the distributor, but the one on the OTHER side of the box) is switched +12V power to turn the ign on.

I'd expect your ign switch is shot and won't secure power to that wire, but I suppose the wire could be shorted/melted to a source of power somewhere in the harness (not so likely but just about the only other thing it could be if you find the switch is good).

It'd be best to check the switch and replace if bad, but failing that you could add an 'emergency shutoff' to the motor by splicing an appropriate switch inline with the white power wire.

Just make sure, if you mount this switch where it'll protrude into the motor, you use a marine-grade, spark-arresting type of switch and not just any ol' thing from Rad Shack etc. Don't want any nasty sparks igniting fuel vapors inside the motor!!!!

HTH..........ed

Re: '71 merc 135hp won't shut off!!??

whwt do i have to do to replace the switch? do i jjust cut the wires and take out switch and splice them back on? I don't want a big project =just want to shut the darn thing off when i want to. thanks again

Re: '71 merc 135hp won't shut off!!??

On the MerControl that came with that motor, the wiring harness was soldered to the ignition switch. You will therefore need to cut the wires (or unsolder them), and then solder the wires to the new ignition switch. Use some flux and rosin core solder.

Re: '71 merc 135hp won't shut off!!??

Chris1956 said:

On the MerControl that came with that motor, the wiring harness was soldered to the ignition switch. You will therefore need to cut the wires (or unsolder them), and then solder the wires to the new ignition switch. Use some flux and rosin core solder.

Click to expand...

Just use rosin core solder. (electronic variety, not hardware store stuff)

Do not use any paste flux. That is acid, (or acid salt) based and will corode and cause all kinds of grief in the future.

I personally use a eutectic (67 sn/33 pb) active resin core solder. One of the lead free (tin-silver) solders would also work fine.

hope it helps
John

Re: '71 merc 135hp won't shut off!!??

I actually had the controls replaced last year, so the switch is now in the dash. i'd have to go under the dash to replace it, but i guess i'd still have to cut the wires and re-solder? I was hoping there might be simpler way to just shut the engine down. Otherwise, i might be better off to have a tech replace the switch. i hate to sound cheap, in just hate to spend money on this old-timer if i can avoid it. thanks again, art

Re: '71 merc 135hp won't shut off!!??

Check your under-dash wiring, make sure you don't have any wires touching each other. I'd say the most likely point of failure would be under the dash.

Otherwise, "Plan B" it and install that switch inline with the white wire back at the motor. That'll shut 'er off fer sur!

Just remember that as long as you have this condition, the CDI box is "hot" all the time and the motor could inadvertently start. It's also continually draining the battery, whatever small amount of "juice" it takes to run the CDI box.

I'd recommend disconnecting the positive battery cable until you get the problem resolved.

HTH.......ed

Re: '71 merc 135hp won't shut off!!??

sorry, but could you please guide me step-by-step through the process of splicing that switch in? I think i can do it but i don't want to screw it up. Also, where can i get the switch and what should i ask for? thank you so much for the help, art

Re: '71 merc 135hp won't shut off!!??

Here's some examples of marine-grade, sealed electrical switches that would be appropriate for your application:

http://www.wiringproducts.com/index1.html

First you'd need to locate a place on the motor to mount the switch. Choose a location somewhere on the front part of the motor so you'll be able to reach it from inside the boat. Then drill away (cringe!) and mount the switch.

Once you have the switch mounted, disconnect the +12V white wire at the side of the CDI box and connect it to the switch. If it's not gonna reach, splice in a length of wire. Be sure to insulate any splices you make.

Then run another wire from the switch to the same terminal on the CDI box where you just disconnected the white wire.

Note that normal convention for the switch would be "open/off" is switch lever down, and "shut/on" is switch lever up.

That's about all there is to it! You'll need a set of wire strippers/crimpers and appropriate crimp-style wire connectors to match the switch's connections. And some shrink sleeving over any exposed splices or connectors helps to keep things tidy. This electrical stuff is commonly available at your local Rad Shack or most auto parts stores.

HTH, now you can Git 'er Dun!!!!!!..............ed

Re: '71 merc 135hp won't shut off!!??

you need to find the problem and fix it you are getting a cross from a hot wire
what was suggested on a adding a switch on the motor is rigging. "rigging is for sail boats"

Re: '71 merc 135hp won't shut off!!??

ok, I went out and got the switch and wiring. I just got a marine-grade toggle switch from napa, the guy said it should work. it has 3 terminals(on-off-on?). But now i'm thinking would it be easier to replace the ignition switch(assuming it's bad). Boaters World has a push to choke switch that looks just like mine with the wire leads so i could just match up the wires. it's kind of a pain working under the dash though. if it still doesn't work i could resort to 'plan B' and install the cut-off switch at the motor and return the ignition switch to the store. let me know what your opinion is. thanks again for all the help, art

Re: '71 merc 135hp won't shut off!!??

Okay, I hooked up the cut-off switch as instructed and just have to hook up the battery to see if it works. one thing i'm not positive about is the toggle switch has 3 terminals. i attached the wire rom the motor to the top terminal and the wire back to the cdi to the middle one- i assume the top(and bottom)are on and the middle is off. hope i did it right. let me know what u think, thanks, art

Re: '71 merc 135hp won't shut off!!??

It's a single pole double throw switch. Use the center and either of the outer connectors.
Here's a diagram.

Re: '71 merc 135hp won't shut off!!??

thanks for the help!