88HP Johnson won't rev up

[M Carroll]

I've got an '88 Johnson 88. It cranks and idles fine. It's OK at low load, up to maybe 1500-2000 rpm. But from there on up, it's dead. At WOT, it acts like it's not getting enough gas. It acts like it's really bogged down and won't go above about 2500-3000 rpm. But, if I press and hold the choke, it picks right up. It sometimes runs smoothly for several seconds, sometimes seems to shutter a bit, always does better. But when I release the choke, it dies right back off. I looked at the carb linkages, etc for obvious problems. I swapped tanks. I played with it, spit on it and cussed at it to no avail. I saw some good info in a post titled 88HP '89 Evinrude. I'll check the things advised there. Any other ideas? Bad gas? Water in gas? Failing electronics? Thanks. Mark. <br /><br />PS. This is my first time visiting this forum. Looking through the posts, it seems you are a very sincere and helpful group.

 

[kart33]

Re: 88HP Johnson won't rev up

Sound as if the fuel pump is having a problem. If not check the height of the carb floats.

 

[pennyanman]

Re: 88HP Johnson won't rev up

also look at high speed jets, My motor ran exactly the same way last week. I rebuilt the carbs and found a lot of green silty paste in all four high speed jets. Motor runs perfect now.

 

[M Carroll]

Re: 88HP Johnson won't rev up

Let me tell you what I found today. I don't know exactly what to call these parts, but I'll try to be descriptive but brief. The throttle operates a big (3 or 4") plate which has a slot in it. As you increase throttle position, this plate pivots forward. This causes the non-concentric slot to move a lever which is connected to the spark advance mechanism. The bushing on the bolt which rode in the slot was broken and lying on the motor base. This allowed the parts to move +/- 1/2" in the slot. This meant the timing was not being advanced properly as the throttle was opened. Moving that advance lever just a little bit at any engine speed made a tremendous difference in how the motor was running. To add to the story, the boat place gave me the wrong part. I had to improvise. I ended up using a piece of 1/4" fuel hose to act as a bushing. The boat now runs fine in the yard, but I haven't yet taken it to the water to open it up and ensure I have actually corrected the problem. What do you think? Does this sound like I got it? Or am I going to find more gremlins? I'll re-post after I try it out - probably this weekend. Mark.