1996 johnson 25 hp runs good but won't idle

**ichabod** · 04-30-2017, 08:49 PM

is there any way to set idle speed. will seafoam help idle problem carb has been cleaned?
?

**doggone** · 04-30-2017, 09:01 PM

probably the low speed jet...I just had the same problem with a 9.9 Johnson I loaned to my son...he let it sit too long and the gas went bad. I cleaned out the tank and replaced hoses...took apart everything I could on the carb that did not have the EPA tamper proof screw ( you need one to get to the low speed jet on my 2003 model ). Anyway after all the cleaning and new fuel and hoses I started it and it wouldn't idle because the low speed jet still had something in it. I started looking around to buy a screwdriver to fit...but in the meantime I started it everyday and ran it for a little while. On the third day it must of dissolved whatever was in the low speed jet because it started running like new. I had soaked the carb in cleaner and blew it out with air...still took a few days with new gas to finally break out.

**Archerguy1** · 05-01-2017, 01:35 PM

If memory serves me, and I am getting old, the carb may have a plastic top cover , similar to the 40-70 HP carbs. If it has a plastic top cover, remove it and look at it holding it up as it came off. Does the bottom look bowed, if so replace it with a new top cover and gasket, ethanol gas cause these to bow and it allows air into places it's not supposed to be, causing a lean condition, this won't idle , or it could slow gas to get into places, causing a rich , flooding condition, either way motor won't idle

**scout-j-m** · 05-02-2017, 11:36 AM

Originally Posted by Archerguy1

If memory serves me, and I am getting old, the carb may have a plastic top cover , similar to the 40-70 HP carbs. If it has a plastic top cover, remove it and look at it holding it up as it came off. Does the bottom look bowed, if so replace it with a new top cover and gasket, ethanol gas cause these to bow and it allows air into places it's not supposed to be, causing a lean condition, this won't idle , or it could slow gas to get into places, causing a rich , flooding condition, either way motor won't idle

Along those same lines.... I bought a used 1992 15hp Johnson last summer it had similar issues. 1992 was the end of that motor style/design. A mechanic in the past had replaced the plastic top of the carb with a post 1992 model one which had a side idle mixture screw instead of the one that came out of the front like it should have. As a result the idle mixture screw did nothing and the motor was running super rich. Bought a new plastic top, gasket and needle and a used mixture knob and now it runs great.

So my point is check the parts numbers of your plastic top (as well as the carb itself) to see if they match the motor model year.

Thread: 1996 johnson 25 hp runs good but won't idle

Thread Tools

Display

1996 johnson 25 hp runs good but won't idle

Tags for this Thread

Posting Permissions