1971 Mercury 7.5 HP intermittent spark, phasemaker ignition

FbnLny

Recruit
Joined
Jan 20, 2023
Messages
4
Hello everybody,

I adjusted the points, replaced the insulator blocks, replaced the coils and redid the whole wiring. I tried running the engine the other day and it only started and stayed running at WOT, anything less and it turned off.
I noticed, that the spark plugs don't fire reliably, cyl. 1 used to, but doesn't anymore for some reason, cyl. 2 only fired occasionally (with NGK BUHW-2 plugs). When using BUHW plugs (shorter gap) both plugs fire reliably every time.

To me, reliable firing at shorter gab sounds like weak spark, or could it just be the low speed I am cranking the engine at?
 

FbnLny

Recruit
Joined
Jan 20, 2023
Messages
4
I managed to solve the problem:
Regapping the points wasn't enough, I cleaned them up with 500 grit sandpaper, now I get good spark on the correct plug
 
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