'72 evinrude 100 won't start

[fishdog4449]

Hey guys,
'72 evinrude 100 hydroelectric shift has some starting issues. She cranks, and usually fires one or twice then dies. Sometimes it almost sounds like a backfire through the prop. A few times I managed to get it running for a few seconds but ran very rough. Thought it might be lean condition so rebuilt the carbs and fuel pump and new fuel lines still same problem. Going to get the clymer and check for spark today but other than that any ideas?
She ran fine a few weeks ago.
thanks in advance this forum is great!!

 

[JB]

Re: '72 evinrude 100 won't start

Check your flywheel for a sheared key.

 

[Joe Reeves]

Re: '72 evinrude 100 won't start

If flywheel has been removed, the flywheel nut must be torqued to 105 foot pounds upon assembly.

Did you manually clean the brass high speed jets with a piece of single strand wire? If not do so as solvent really doesn't do that job thoroughly.

Also clean the small brass slow speed jets with the proper size drill. The size is marked on the sides of the jets.

 

[fishdog4449]

Re: '72 evinrude 100 won't start

Thanks Joe and JB,
The flywheel and key are A-ok. I did find something wrong with looking at the engine today. The purple wire running from the pulse pack which is supposed to connect to the purple wire running from the ignition switch and the thermo switch was instead connected to an empty terminal post connected to nothing. Could this have been the problem?
Also, there are two identical black and white leads connecting the pulse pack to the stator sensor, does it matter which is connected to which (connection between sensor and pack)?
thanks guys!!

 

[Joe Reeves]

Re: '72 evinrude 100 won't start

That purple wire that wasn't connected, check it with a volt meter. If with the key OFF, no voltage exists at that wire BUT with the key ON, voltage does exist, then it should be connected to the terminal that leads to the purple wire connnection. This would properly enable 12 volt to be applied to the pulsepack when the key is ON.

As it stands, you are simply applying voltage somehow to the pulsepack when the ignition switch is in the START position, possibly thru a diode between the starter solenoid and that pulsepack purple terminal.

The two black/white wires merely make a connection thru the timing sensor. If memory serves me correctly, it doesn't make any difference how they're connected. It simply completes the circuit.

 

[fishdog4449]

Re: '72 evinrude 100 won't start

Joe,
There was indeed 12V with key on and nothing with key off. If the pulse pack was not getting power, perhaps thats why the engine tried to start but as soon as starter was let off she died.
Or at least thats what I'm hoping.

 

[Joe Reeves]

Re: '72 evinrude 100 won't start

With the key OFF, you would indeed NOT have any voltage. Hopefully you meant as I indicated above that there was voltage in the START position BUT no voltage in the ON position. In the OFF position, everything is OFF.

 

[fishdog4449]

Re: '72 evinrude 100 won't start

"If with the key OFF, no voltage exists at that wire BUT with the key ON, voltage does exist, then it should be connected to the terminal that leads to the purple wire connection. This would properly enable 12 volt to be applied to the pulse pack when the key is ON."
This is what I have now.


This agrees with the Clymer wiring diagram which shows that that purple powerpack wire should be connected to the two other purple ones(ignition switch (+12) and thermo switch) at terminal nine. I think what happened was that when I put all electronics back on after painting the powerhead I misplaced that purple wire.
I'll double check everything again and try to fire it up tomorrow.

 

[fishdog4449]

Re: '72 evinrude 100 won't start

Also, the motor is completely missing what Clymer calls the "Clipper Circuit Assembly"
...can anyone explain what this is and why I could be missing it?

 

[Joe Reeves]

Re: '72 evinrude 100 won't start

The "Clipper Circuit" originally (supposedly) prevented power surges of the charging system from reaching the pulsepack. It created more problems than it cured. OMC issued a bulletin to have it removed and to reroute the wire to povide voltage to the pulsepack. No doubt, this is why that voltage wire wasn't where it shsouldd have been.