1977 johnson 70hp

[doug sagner]

will start up and idle great.

will start up and idle great. put it in gear runs good up to 15mph.open it up full speed go's up to 27mph then engine die's out. think it could be the power pack. thank you

 

[sparky]

Get an inductive pickup timin

Get an inductive pickup timing light. Hook it up to #1 cylinder and observe the flash when the engine dies. If it continues sparking #1 ignition is not the problem. Repeat with #2 and #3. Report your findings.