1991 90 hp Idle screws

allegiance

Cadet
Joined
Jun 11, 2005
Messages
12
I just rebuilt the carbs on my 1991 90hp force outboard. It has a 3 carb set up. I am having trouble getting the engine to idle. What is the best way to get the idle screws on all three carbs in sync so the engine runs smooth?<br /><br />Thanks, john
 

Realgun

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Jul 31, 2003
Messages
2,484
Re: 1991 90 hp Idle screws

From what I understand you lightly seat the screws clockwise then turn them 1 full turn out.<br /><br />Do this for all three carbs. <br /><br />See if it starts. If it starts turn the screws 1/4 out again should speed up. Let it idle 30 seconds to stabilize then do another 1/4 till it starts to die. Turn clock wise 1/8 till it runs slow they back out to where you in the middle of fast and slow. Better to be a bit out than in.<br /><br />Hope this helps.
 

allegiance

Cadet
Joined
Jun 11, 2005
Messages
12
Re: 1991 90 hp Idle screws

I was told by a friend that the screws may have a preset industry standard for length they are turned out. Is this true/
 
Joined
Aug 4, 2005
Messages
17
Re: 1991 90 hp Idle screws

When I rebuilt my carbs and tried to start it, it wouldn't hold an idle either. Ended up being that I had some fuel lines (and bowls) in the wrong places. Fix it and she fired right up. On my carbs the idle screws were 1 turn out for both of them. Also, did you take out the idle tubes in the carbs? If so, they have to be put in the same depth as they were before, otherwise the motor will not idle right. After rebuilding the carbs did you sync the carbs together and adjust the cam to the roller? All these have to be done once you take the carbs off! I'm no expert (believe me) at all and don't claim to be one, these are just the things I went through when I re-built my carbs 3 weeks ago. Good luck! - Mike
 
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