120 johnson jet sizes

F

fpvman

Cadet
Joined
Aug 13, 2011
Messages
12
hey
i have a 1987 120hp johnson i have been having probems with it lately so i took all the carbs off and gave them a good clean out. while doing that i noticed that the jet sizes were different from port to starboud the were
starboard 16 and 33
port 16 and 36
why does the two sides of the engine have different jets and what r the standard ones meant to be? as i want to put the original jets bak in it
cheers for any help
 
F

fpvman

Cadet
Joined
Aug 13, 2011
Messages
12
Re: 120 johnson jet sizes

awsome thanks that helps alot the other site i found would only tell me starboard side jet sizes.
ill order some of them and try it out see if she works better.
why would someone change the sizes to that would you put 140hp jets in at least?
 
A

archcycle

Chief Petty Officer
Joined
Sep 21, 2009
Messages
647
Re: 120 johnson jet sizes

Why do people do the things they do? I just changed out my idle bleeds because there were 3 different sizes and none were correct. Maybe they had a different application for the motor than you're using it in? using it in different conditions like much higher or lower altitude? maybe some shade tree mechanic said "let's re-jet it" and the PO said wow that sounds technical it must be a good idea?

Maybe the different sides came over along with different throttle bodies that someone put on? When in doubt make it look like the parts diagram and factory service manual. That generally solves problems related to previous owners.

Since both carbs match on each side and neither side is correctly jetted I'd check whether the throttle bodies match and also if they're correct for the motor. You frequently see carbs for sale still attached to the throttle bodies and a "this fits 1800-2012" with no mention of what it came off of and what it's set up for.
 
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