1982 70hp Johnson Timing, spark plug questions

South Paw

Seaman
Joined
Apr 10, 2012
Messages
52
Hello all,

I will shortly be replacing the stator and timer base in my engine. I have gone with CDI parts for these items.

I have read various threads in regards to spark plug gaps etc and sticking with forum rules have started a new thread, i'm sure this has been done to death.

Firstly can someone tell me in METRIC what should the gap be set to? I have the NGKs and a set of Champions.

Secondly, i have a workshop manual, but just wondering with the demise of leaded fuel, how does this effect timing etc on this engine?
As i understand it, unleaded fuel degrades faster than the old leaded stuff and if old will effect detonation.

If there is is a thread for setting the timing for this engine could someone link it?

I appreciate all replies as usual this forum has been of immense help.
 

durban

Master Chief Petty Officer
Joined
May 27, 2011
Messages
894
Re: 1982 70hp Johnson Timing, spark plug questions

recomended plug L77J4 , Gap , 0.040 inch , metric 1.01600 mm , after you fitted every thing & pluged all the plugs in , provideing you have not turned the idle ajusting screws . the 2 that are spring loaded by the trigger to the right of it your timeing should be some where near , best to double check , get a timing light connect to spark plug no 1 [top one ] , turn the motor over useing a strong charged battery aim the timing light at the pointer it should fire TDC , mark this with a little white chalk easier to see , when i do the wot timing i disconnect the carb linkage & at idle move the trigger in anticlock wise direction the timing light should then flash on 19 degrees RPM idle should be between 700-750
the 2 spring loaded screws by the trigger turn the bottom one clockwise to advance & anticlockwise to retard
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,589
Re: 1982 70hp Johnson Timing, spark plug questions

The correct plug is a QL77JC4 and metric gap is .7620 (factory spec is .030). Install your new parts and take a dial indicator and check to see if timing pointer is at TDC. Remove the spark plugs and ground #1 plug. Take a timing light and attach to #1 plug, remove the throttle cable and advance it to WOT position. Use a remote starter or have someone turn the engine over and check timing. If timing needs to be adjusted it is set by loosening the lock nut on timing screw behind #1 carb, screw in to retard and out to advance the retighten lock nut. With todays fuel I usually retard timing 2? from factory spec's. Reattach cable and plugs,start engine and if on a hose set the idle rpm to about 1000-1100rpm as when you get it in water the backpressure will cause the RPM to drop down into the 750-800 range...
the 2 spring loaded screws by the trigger turn the bottom one clockwise to advance & anticlockwise to retard
?????????
 

South Paw

Seaman
Joined
Apr 10, 2012
Messages
52
Re: 1982 70hp Johnson Timing, spark plug questions

Thankyou very much guys. I have the QL77JC4's.
 

durban

Master Chief Petty Officer
Joined
May 27, 2011
Messages
894
Re: 1982 70hp Johnson Timing, spark plug questions

the 2 spring loaded screws by the trigger turn the bottom one clockwise to advance & anticlockwise to retard
the reason why is because when you turn the screw in clockwise the timer base moves in anticlockwise direction when the flywheel comes round in a clockwise direction the groove on the inside of the inner diameter is gonna trigger the sensor off to spark before the piston gets to top dead center , check it out for yourself .......?
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,589
Re: 1982 70hp Johnson Timing, spark plug questions

These screws do nothing for the max timing... the top screw is the throttle stop to keep butterflys/shaft from"camming over" or going past the horizontal position and lower is the idle adjustment screw...
 

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South Paw

Seaman
Joined
Apr 10, 2012
Messages
52
Re: 1982 70hp Johnson Timing, spark plug questions

Thanks for the pics Faztbullet, very helpful.
 
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