1972 100hp johnson power problem

[firecapt221]

alright guys i need your input...i got a 72 100hp johnson runs great . starts with a flick of the key. when in neutral engine will rev up as it should sounds real nice. but when i go forward it doesnt rev up as it does when in neutral and sounds as if i am only at half speed with throttle all the way down. it is only getting to about 15 mph it is really frustrating. does any one know what my problem is here.any and all input will be great . thnx

 

[Monte1961]

Re: 1972 100hp johnson power problem

Have the right prop installed?

 

[Will Bark]

Re: 1972 100hp johnson power problem

Use an inductive timing light and see if you are dropping spark on any of the cylinders.

 

[Daviet]

Re: 1972 100hp johnson power problem

You should start by checking the spark and compression. Does it idle properly, maybe you have some high speed jets plugged. Does it help if you pump the primer bulb when the problem is happening?
You really shouldn't rev the engine very high without a load on it.

 

[firecapt221]

Re: 1972 100hp johnson power problem

alright, i do have the correct prop installed and timing is good. i pulled the plugs and there was a buildup on them, does this mean my carbs need to be redone also?

 

[Monte1961]

Re: 1972 100hp johnson power problem

Not necessarily. Check compression first and get us the results for each cylinder, IE: #1 110psi #2=100psi ect,ect,ect. That will helps tremendously. Post back and good luck.