28 hp johnson won't open (rev)up

[Tom Saxby]

I have a 1986 (i think, model number j28elcdc serial # e6203803) 28 horse special. I just got running after a couple years sitting. It starts fine and idels around great but when you try to open it up it starts to then bogs down and sometimes quits or runs at a low throtle. I am not sure if it's the carb or fuel pump. Is there any way to tell? Also how hard is it to change this motor to tiller control? what would it cost?

 

[jtexas]

Re: 28 hp johnson won't open (rev)up

welcome to the forum.

What you are describing is a classic symptom of gummed up high-speed jets.

How to tell: process of elimination.
easy stuff first:
Is the fuel fresh, and free from debris and water?
Does the fuel line hold pressure?
Is the fuel tank vent open and clear?
Do you have the correct champion spark plugs set at the correct gap?

Next, compression test
Then spark test. set your tester for 7/16". don't use spark plugs to test spark, it won't tell you anything.

If everything checks out, then a carb rebuild is in order.