1988 johnson gt100 carb adjustment

[Nicktr23]

Hi, i just acquired a new to me outboard, johnson gt100 1988. I'm not new to outboard but i currently dont have a manual for this outboard. I wanted to get it running before investing more money into it. Anyways, normally when i worked on outboards before, the carburetor will have low idle screw adjustment for the carburetors. But as i was pulling off these carburetors to clean them, i didnt see any idle speed adjustment screws. Do these carb have adjustment in the carb beside adjusting the float?
Also, while the engine is running, i pulled off the spark plug one at a time, i notice that when i pull the top spark plug, there is a change in engine response. However, when i pulled the bottom plug, no change in engine response. This led me to believe that at low rpm, the bottom cylinder on each side is not utilized??? Any insight greatly appreciated. Thank you.

 

[racerone]

Wrong-----It runs on 4 cylinders all the time.-------I would start with a compression test.-------No mixture adjustment needed on those carburetors.

 

[Nicktr23]

Thank you.

 

[Nicktr23]

I didnt a cold compression check first time cyclinder 2, 1, 3 all 100, cylinder 4 is 80. But this engine havent run in 2 years. I'll recheck compression again. Doing the cylinder drop test, pulling spark plug from cylinder 1 and 2, the engine reacted. Pulling plug from 3 and 4 had little reaction. Now im curious if the bottom carb is not working properly? The bottom carb is providing fuel to cylinder 3 and 4 correct? Also, i checked spark on all cylinder, all have good spark.

 

[racerone]

Remove bypass cover ( 6 wee bolts ) on the cylinder with lowest compression.-----You can then look at piston and rings.----Or remove the cylinder head for inspection.----Lucky you if it is a blown head gasket.----I think you will see why it was " for sale " after this inspection.

 

[Nicktr23]

Those compression numbers are when i first brought the engine home. After getting it running, i did another compression check. Compression are 105 for cylinders 1,2,3 and 110 on cylinder 4. I had to advance the timing to start the motor and once it's warmed up, i dont have any problem starting it. But... it is making this constant knocking sound at idle. I'm uploading a video on youtube soon. I dont believe it is a few issue anymore. I pulled out all spark plugs and did the dowel knock test and there is slight movement on cylinder 1. The knock is coming from the flywheel and now im unable to remove the flywheel for inspection.

 

[Nicktr23]

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