57 Johnson mixture mess up

[Lalli]

Hello, we have a 57 Johnson, 18 horsepower motor. It was running great...until my boyfriend decided to "clean it up" by taking all the knobs off the front, wiping it down, and putting them back on. Now, she only runs at about 1/2 the speed that it used to with a fully open throttle. We think that the "lean - rich" and "high speed - low speed" knobs are in the wrong combination. The top knob can turn 22 times before it is fully tight, and the bottom knob turns 16 times before it is fully tight. The motor won't start with either of them fully tight so we're wondering if there is a certain amount of turns each should be to work in concert with each other. Also, depending on where the knobs are set, after starting, the motor sputters and dies. I hope someone out there has an idea about what I'm talking about and hopefully a solution to our self-induced problem. Thanks for all your help so far!

 

[Xcusme]

Re: 57 Johnson mixture mess up

OK, Try this.....courtesy of our good friend J. Reeves.

Depending on which carb you have, pick one of the following.

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8
turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to
respond. As you turn the valve in, the rpms will increase. Lower the rpms again to
where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back
(sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4
turn, you'll find the smoothest slow speed setting.

When you have finished the above adjustment, you will have no reason to move
them again unless the carburetor fouls/gums up from sitting, in which case you
would be required to remove, clean, and rebuild the carburetor anyway.
--------------------------------------------------
(Carburetor Adjustments - Two Adjustable N/Vs)

Initial settings are: Bottom high speed = seat gently, then open 1 turn out. Top slow
speed = seat gently, then open 1-1/2 turns.

Setting the high and low needle valves properly:

NOTE: For engines that DO NOT have a shift selection, obviously there is no
NEUTRAL position. Simply lower the rpms to the lowest setting to obtain the low
speed needle valve adjustment.

(High Speed) Start engine (it will run pretty rough), shift into forward gear, take up to
full throttle. In segments of 1/8 turn, waiting for the engine to respond between turns,
start turning in the bottom high speed needle valve. You'll reach a point whereas the
engine will either start to die out or spit back (sounds like a mild backfire). At that
point, back out the needle valve 1/4 turn. Within that 1/4 turn, you'll find the
smoothest setting.

(Low Speed) Slow the engine down to where it just stays running. Shift into neutral.
Again in segments of 1/8 turns, start to turn the top needle valve in. Wait a few
seconds for the engine to respond. As you turn the valve in, the rpms will increase.
Lower the rpms again to where the engine will just stay running. Eventually you'll hit
the point where the engine wants to die out or it will spit back. Again, at that point,
back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed
setting.

When you have finished the above adjustments, you will have no reason to move
them again unless the carburetor fouls/gums up from sitting, in which case you
would be required to remove, clean, and rebuild the carburetor anyway.

--------------------
Joe (30+ Years With OMC)