Home › Forum › Ask A Member › 1966 Evinrude 18hp… cough sputter cough! › Re: 1966 Evinrude 18hp… cough sputter cough!
Like everyone says, sounds like the engine is running on one cylinder, the other kicks in occasionally which explains the change in "pitch" and power for a second. Hopefully, this is just an ignition problem, could be something as simple as a bad plug. Just cuz the parts are new, doesn’t mean they are any good.
Another relatively cheap diagnostic tool are those inline neon spark testers, you can get them at most parts stores/Sears/Harbor Freight.
Run the engine with two testers inline between the plugs and coils. Have an assistant drive while you monitor the testers, probably easier when the sun is going down. Keep in mind that a bad plug could cause the tester not to light as well.