50 HP 1974 Evinrude spark timing power

" Got an old motor and 14ft bo

" Got an old motor and 14ft boat. Motor was running rough, with apparent low power esp at speed. I was about to replace plugs (the old ones seemed a bit oily), but the manual calls for UL-77 (I recall), but in the motor they were QL78JC4. Which should I use?

Further, I was checking why it might be low power/rough idle, and pulled the top wire - motor started and ran the same on the bottom cylinder only. Tried to start and run on top cylin only - nothing. Joe once mentioned top cylinder are easily affected by armature base problems under flywheel - is this possible a timing issue? Compression? Spark seems to the the same on both cylinders when checked at spark gap.

Any comments/suggestions on proper plugs and low power?

Thanks,

astrong "

"Astrong.... S/Plugs for that

"Astrong.... S/Plugs for that engine should be either Champion L77JC4 or QL77JC4 plugs set at .040 . The original plugs were Champion UL77V plugs but they have no heat range and are subject to fouling.

If you have compression and spark, the remaining items that would be affecting your engines top cylinder would be fuel.... I'd suspect that your top carburetor is fouled.

I never said that the timer base would affect the top cylinder. I said that a sticking timer base would result in a retarded spark advance situation.

Joe "

Thanks for the info Joe. I&#

Thanks for the info Joe. I'll try new plugs/proper gap.

The comment on the armature base was from something you had said in the thread "40 HP Johnson (1975) bogging down. Need help" Sorry to mis-quote you on mine. But does a top cylinder normally miss fire or otherwise fail more often than the bottom on these older OMCs??

Thanks again.

"Astrong.... To possibly contr

"Astrong.... To possibly contradict myself, if the "Timer Base" sticks.... the engine runs at a retarded spark advance. This is usually associated with the engines that incorporate the smaller diameter timer base assy. I've yet to see any of this type rock or move sideways though.

The larger diameter timer bases were/are called "Armature Plates" and are associated with the smaller horsepower engines. The center portion of these plates can become worn which allow it to move sideways slightly, and the retaining rings also wear which allow the plate to rock..... and that does for some reason seem to always affect the top cylinder.

So in effect, you were correct about my quote as I really didn't define the difference at the time. My apologies if my reply seemed somewhat critical.

No, there is no preference of failure pertaining to the top cylinder failing more often. Just seems that way. Let me know how you make out.

Joe"