1971 johnson 125 hp electric shift fuse blows at 1500 rpms

rekamlias

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1971 johnson 125 hp electric shift fuse blows at 1500 rpms or more. I do not see a regulator on this electric wiring digram that came with the manual. Any guess at why she blows the fuse when she i have the rpms up?
thanks in advance for your help
rekamlias
 

F_R

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Re: 1971 johnson 125 hp electric shift fuse blows at 1500 rpms

Throttle linkage rubbing on a wire somewhere?
 

rekamlias

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Re: 1971 johnson 125 hp electric shift fuse blows at 1500 rpms

i have been all over this thing i do not see any wires chafing or cracked/shorted. But when I turn the key to the on position the control box diode gets hot. I think the push button controler for the engine is incorrect model for this engine. The key switch is probably bad. I have a shifter that may work but if i hook a new key switch will I have to install diodes. What do the diode do and what voltage are they. Is there a wiring diagram just for the key switch and shifter available with diodes in it?
Thanks in advance
 

F_R

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Re: 1971 johnson 125 hp electric shift fuse blows at 1500 rpms

There are two sources of +12v supply to the shift switch, both sources have blocking diodes. The first source is the ignition switch. The second source is the alternator. The ignition switch source is working as evidenced by the heated diode. The diode is passing excessive current which is why it is heating up. I suspect you have a short to ground somewhere in the alternator source. It gets pretty complicated at that end.

As a first step, I suggest you disconnect the purple/green stripe wires at the terminal block on the motor and see if that stops the diode overheating. Then we can go from there.

Send me a PM with your e-mail address.
 

rekamlias

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Re: 1971 johnson 125 hp electric shift fuse blows at 1500 rpms

I have a short in the one of or both shift solenoids. When I unplug the shifter plug (3 connector) the breaker does not blow. Yes I put a 20 amp circuit breaker at the fuse locatation. When I turn the key to the on position the breaker blows in 6 to 8 seconds with the shifter wires connected. She runs great with the shifter unconnected. I put an impeller into the engin. last weekend and I must have shorted a or both leads to the shifter solenoid/s. I hope I do not get the dumb *** award for my impeller install. Wish me luck I will let you know how it goes. Thank you so much for your help and input.
Mike
 

F_R

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Re: 1971 johnson 125 hp electric shift fuse blows at 1500 rpms

The purple/green wire going to the connector comes from the Alternator stator, altrnator rectifier, and clipper circuit. Any one of those can be shorted to ground and blow your fuse. Yes, so can the shift solenoid wires.

That's why I suggested disconnecting the purple/green wire at the terminal block to see if the fuses keep blowing.
 

llilillill

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Aug 8, 2007
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Re: 1971 johnson 125 hp electric shift fuse blows at 1500 rpms

I guess I earned the ~Dumb***~ award then. Just had the same problem... smoking shift wires after pulling the lower unit to change the solenoids. Checked the green wire with an ohmmeter and found it shorted to ground... needless to say, it's very easy to pinch the wires between the solenoid housing and the lower unit mounting bolt hole, even after being very careful not to do just that!

I ended up pulling it back down and taping the wires over top of the solenoid housing to facilitate installation. If the wires come anywhere near the side of the soloenoid housing while you're mounting it back up, they get caught very easy... only about an eighth inch of clearance there.
 
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