I have an old but very reliable 60 something johnson 70HP, It runs well in Denver 5,000 ft in altitude. When I take it up above 7,000 ft it wont turn the RPMS to move faster then a small snail. I am running a 13 3/4 by 15, Tried a lightweight composite prop same results. Any suggestions? I tired adjusting the jets but with the three seperate carbs everbody I have talked to says try the prop angle first.
