Reply To: Weak spark on 1973 20 Hp Johnson

[Don]

First, please don’t every try to swap throttle or choke shaft components by removing the butterflies. The butterflies are staked in place for a good reason, you sure wouldn’t want the screws to get sucked out and gobbled up in the powerhead….Plus, the butterfly could get jammed in the WOT position, usually at the most dangerous moment.
What I’m hearing you say is that your engine is hard starting when cold, but once warmed up it starts fine, do I have it right?
If so, I would have a look at the choke linkage, some of these designs are not the greatest…Some of the chokes rely on the choke knob bushing to hold the choke completely closed….So, I would have an assistant pull the recoil while you ensure the choke is completely closed.
The carbs from the 1981 70hp will not work on your 20hp….Completely different design, even though it might “bolt up” OK.