'93 Johnson 25HP RETS won't idle below 900RPM

[Tucker99]

Gents,
This was an estate sale, latest registration 2014. Ran very rough when purchased. Good compression. Changed water pump, fuel pump, thermostat, new plugs, and wires, and rebuilt carb. Idle screw out 1-1/2 turns. Primer test fine, no leakage, good spark, link and sync, throttle plate horizontal at WOT. Difficult to start, must be very careful with the primer, motor floods easy, won't stay running. Any ideas guys?

 

[brim_buster]

I adjusted my buddys idle screw out 1/2 turn from seat and it runs like a champ. I thought like you 1 and 1/2 but couldnt get it run. So I started from seat and slowly adjusted it out till it found the sweet spot.

 

[oldboat1]

The motor will not run (should not run) with the idle mixture needle closed. If using 1 1/2 turns open as the initial setting, start the engine and warm it up if you can, then adjust clockwise 1/8 turn at a time letting the engine catch up between adjustments. When the engine stalls or lean sneezes (sounds like a mild backfire), turn the needle counter clockwise about 1/4 turn. This should be close to the ideal position.

[edit. Running on muffs will yield higher idle rpm that on a boat or in a barrel. Also, adjusting for a leaner air/fuel mix will normally (properly) raise rpm -- reduce them to 650/700 with the throttle idle adjustment.]

 

[Tucker99]

Thanks, testing is done in a barrel. Engine floods easy. I'm not familiar with a primer and following instructions. Pull in and out once and leave in the "on" position (partial out) for a short time, then push it in, is this the correct procedure? Is idle adjustment only done with the idle screw? The FSM says to adjust idle under the cowl at the throttle cable using the the cable connector on the cable end. I set the distance from the cable sleeve to the connector at 1-3/4" and then sync & link. When the motor stalls, I have to keep wicking it and give it full throttle to start it again. How is the best way to check for air leaks? It's behaving like there is a huge vacuum leak somewhere. When rebuilding the carb, I'm wondering if I pounded the round discs in tight? Thanks...

 

[Newyota]

Thanks, testing is done in a barrel. Engine floods easy. I'm not familiar with a primer and following instructions. Pull in and out once and leave in the "on" position (partial out) for a short time, then push it in, is this the correct procedure? Is idle adjustment only done with the idle screw? The FSM says to adjust idle under the cowl at the throttle cable using the the cable connector on the cable end. I set the distance from the cable sleeve to the connector at 1-3/4" and then sync & link. When the motor stalls, I have to keep wicking it and give it full throttle to start it again. How is the best way to check for air leaks? It's behaving like there is a huge vacuum leak somewhere. When rebuilding the carb, I'm wondering if I pounded the round discs in tight? Thanks...

Go on you tube and search “Finding Vacuum Leaks”.These will be used on cars,but can be applied to anything.You will see how it is done.I used the method Shown and it worked great.