"The 1977 6hp Evinrude/Johnson
"The 1977 6hp Evinrude/Johnson calls for Champion QL77JC4 or L77JC4 plugs, gapped at .040. The "Q" indicates a suppressor type plug which is used to quiet interference in any electronic equipment one might have onboard. Use no other type spark plug other than these!
Leave the fuel pump hoses attached but remove the two pump retaining screws. Now, install nuts on those two screws and tighten them so that the fuel pump is securely tightened together. Pump the fuel primer bulb. If any fuel leaks from the small hole in back of the fuel pump, the diaphram is faulty in which case, replace the fuel pump.
Assuming the fuel pump is okay or you've installed a new one. check the compression. Note that the fuel pump must be okay and installed in order to check compression on that model.
One may wonder why the pump must be installed. This 6hp model operates with the compression of the engine. If the fuel pump is faulty or removed, the compression of the related cylinder will be low or non existent.
Should fuel exit the carburetor when the primer bulb is pumped up hard, re-work the carburetor.
Double check the spark with the spark plugs removed. At cranking speed, the spark should jump a 7/16" gap with a strong blue lightning like flame.... a real SNAP!
Let us know what you find pertaining to the compression and spark.
Note that using the spark plugs to check spark is a waste of time, the 7/16" gap is most important.
(Spark Tester - Home Made)
A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.
Using the above, one could easily build a spark tester whereas the!y could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:
(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.
Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.
Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.
Note: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.
When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.
I assume that you're helping a friend and not speaking about yourself. If so, sorry to hear about his cancerous problem and wish him well, and I congratulate you on taking the initiative to be of service to help him in his time of need."
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