1977 85 hp johnson bogs down when trying to throttle.

[Khris]

I have a 1977 85 hp johnson that ran fine the first few times I went out.The last time i went out on the river it ran fine for a minute then lost power at full throttle.Idles fine with ear muffs on at home,but on the river it barely runs.Need help with this problem.

 

[racerone]

They all " sound fine " on a hose.--------Check compression and check for spark on all 4 cylinders.