for all the johnrude guys

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p-vaugh7

New member
ok. i have an 82 johnson 140 v4. i burnt up the piston on my hold powerhead and now have another power head on it but reused all the old electronics. a problem i have had for awhile even on previous motor is that the tach, when motor has ran awhile will start flakeing around. either peg to 7 grand or bounce the whole sweep of the guage. i have the electronics from the other motor and i swapped out the stator under the flywheel. that did nothing for me. in the process i decided to check all the synchronation of the timing and fuel and all ok but while i was timing at wide open throttle. found that when the tach starts to act up my timing light does not pulse. i work on cars so i know that the power going throuhg the wire is what excite the light to pulse. now when it cuts out the motor does not missfire. it seems when i get it to act up as soon as i move the throttle either way the tach fixes itself for a short burst.. if i go under 4 grand and slowly bring it up to speed at about 4,200 it starts to go crazy again. timing while operating correctly is fine but due to the light i cant tell what it is doing when it acts up.. i have heard that the tach acting up could mean the timing is over advanceing as a result. i am at a lose. wanted tot hear if any one had any types of this problem or knows a fix.
any info is appreciated thanks!!
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The tach normally does not run off the ignition on that engine, it runs off the stators pulse for the charging side. Sounds to me like a magnet issue or stator as that is the common components shared by both in the system. The ignition system in it should be completely isolated from any of the boats wiring with the exception of the black and yellow stripe wire to the ignition switch. I would start by checking your wiring and see if any wires have been crossed as the tach being hooked into the ignition side of the stator could be your issue.
 
yeah some automotive timing lights cut out somtimes, i use a blue point that is self powered and it never misses beat and like SP said ignition and charging are two diff things on the stator. it really sounds like your rec/reg is out or going out. check for AC volts from the two yellow wires from the stator and see if you have AC volt and if you do its either the tach or the rec/reg.
 
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