1993 Johnson 90 HP lean sneeze at idle.

[ronaca88]

Hi guys,

Yesterday I was working on the boat, trying to solve some issues, mainly in the fuel pump. I buy the repair kit of the fuel pump and the carburators. I work 5 hours on the boat cleaning grease, rebuilding carburators, rebuilding fuel pump and greasing shifting cables.

When I finish, the boat fire up at first try, but it seems that I need to look at something more to change because it is sneezing like coughing and attemp to stop all the time at idle.

Any clues what I should look at? I plan to change sparks today and all the battery wiring because is corrode.

Here is a link to a short video when is sneezing after the rebuilding maintenance.

Sec: 13
https://youtu.be/FCV_bSnQANM

 

[racerone]

First thing to do is to post results of a compression test.

 

[ondarvr]

The link to the video doesn't work for me, but if this just started after the rebuild I would look at a dirty carb. While its at idle put your hand over each carb until it runs correctly, this will tell you which carb to look at.

Low compression can also do it, I chased a lean sneeze for a couple of days before checking the compression and finding one at 40psi

 

[emdsapmgr]

A lean sneeze on an engine usually means one or more of the idle passages internal to the carb are restricted. This lean condition then results in a misfire every few rpm's. Only way to fix it is to clean the idle passages again. That means a teardown, some Gumout aerosol carb cleaner and some patience. You can't clean dried fuel out of internal passages with an air gun. You need to dissolve the dried gelatin -leftover from dried fuel. You can also get erratic idling if the carbs are not synced. Both sets of carb butterflys have to be completely closed at idle. If one pair of carb butterflys are ajar-even slightly, you will get an erratic idle.