boat engine surging

Another thing that might happen. You might have something in the distributor, if it is mechanical. Worn, sticky, etc, or wrong / weak springs, advancing timing can/ usually increases engine speed. I'm not sure how it works. I assume that something triggers the advance (it unsticks)--advances, engine speeds up, then runs out of idle mixture and falls back. Anyhow examine the dist advance for problems, wear, etc, and re-check timing.

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