1989 Johnson 40hp idle mixture screw settings

Tubes66

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Jun 8, 2017
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So I picked up this boat and motor cheap about 2 weeks ago , and the motor was not running , kid messed with it but had no idea how to work on an outboard . So I bought it , with a compression of 110 on each cylinder . I rebuilt both carbs and took the aluminum plugs out of the carbs and cleaned the idle passages and made sure everything was set right and very clean . I replaced all fuel lines and made sure everything was working and no leaks . The motor was convert from vro to a regular fuel pump and a plug was put in where the vro pulse tube came out . I cleaned and gapped the plugs to .030 . And I had the idle mixture screw set to 2.5 turns , I could really use the rundown on where to set it at a base line and how to fine tune it , the motor will run okay some missing and sputtering with the high idle pulled up some, seems to bog but will rev up and seems to smooth out , but will shut off if I push it down . I'll try to attach some videos if I can .
 

GA_Boater

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May 24, 2011
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Welcome aboard.

Turn the screws in to between 1 1/4 to 1 1/2 out. Final adjust is in the water in gear.
 

Tubes66

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Jun 8, 2017
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Thanks , I'll try that and see what happens . The 40hp is on a Starcraft also , I'm guessing that is yours . I ended up getting it for $350 but it has some other issues to , like a rotten transom board .. it won't let me post a picture
 

oldboat1

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Apr 3, 2002
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oh geez. Transom is a good DIY fix, but think you are stuck with a barrel for working on the idle mix, at least until you can get to the hull repair. Double A/C plywood, using the old one as a template....
 

Tubes66

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Jun 8, 2017
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It's an aluminum boat the transom will take a day to fix. It's just a board about halfway down the inside of the transom
 

oldboat1

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Apr 3, 2002
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yeah, but an important board with a 40 (done a number of them). On some of the Starcrafts, you can extend/deepen the board to help stiffen the transom.
 

JDusza

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Apr 21, 2009
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997
Yes, deepen the board as per oldboat11. Transom function is no joke.
J
 

Tubes66

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Jun 8, 2017
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Yes I understand it won't see water until I fix it that's for sure , and I'm gunna deepen it as far as I can without cutting floor
 
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