Re: 1979 Johnson 140 Carb sync

[Don]

Adam-
How familiar are you with these engines? Do you have a manual? Is all the linkage and throttles moving freely? Is the timer base hitting its full advance stop? Are the throttle plates opening fully?
Most of these synchronization adjustments won’t really affect WOT acceleration that much, they are meant more for smooth running at lower speeds and off idle.
The 140s develop a little more top end power, but sometimes at the expense of midrange performance. Tell us more about the rig, prop style and pitch, along with WOT RPM. These engines need to wind up at WOT or they will perform poorly, especially at midrange. Does the engine have power trim? Does the bow tend to pop up excessively during acceleration? This engine needs to turn up at least 5500 RPM at WOT when properly trimmed.
This is an old engine, that had a lot of compression, not really designed to run on today’s fuels. I would definitely do a compression test. Some of these engines had low octane kits installed, which was mainly thicker head gaskets that lowered compression and performance. The thicker head gaskets are pretty easy to spot.