1973 evinrude 18hp fastwin won’t accelerate

[B.johnson1993]

I have a 1973 evinrude 18hp fastwin, I finally got it running right after replacing some ignition parts last fall and the water pump impeller, then during duck season it got really cold out, and since then the motor will just idle along if you put it in drive, won’t acclerate, just goes maybe 5mph. Goes into reverse fine and the Rpms get high as I give it more throttle, the Rpms when I put it in drive don’t get high so I don’t think it has anything to do with the clutch dog.

 

[RCO]

Do a cylinder drop test to see if you are only firing on one cylinder.

 

[racerone]

No ----Most of think it is running on one cylinder.-----Check for spark that can jump a gap of 5/16" or so on both leads.----Post compression numbers too.

 

[B.johnson1993]

Had a bad spark plug, didn’t know that a spark plug could cause an issue like this