Year 2000 90 HP Johnson mixture adjust

zenwriter

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Nov 1, 2010
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Read Joe Reeves sticky about low speed idle adjustment, but not sure if it applies to my carbs. (Engine dies at lowest forward throttle setting. Recently tuned but needs this tweak).

Joe suggests turning needle valves (1 per carb) 1.5 turns out and then closing valve until engine spits, and then turning 1/4 turn out. Wonder is this applies to my carbs?

Also, what is the sequence? Turn all 4 valves 1.5 turns out and then adjust each one, or start and finish 1 at a time?
 

Joe Reeves

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Feb 24, 2002
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No, that low speed adjustment has nothing to do with the high end. If you're speaking of the engine dying, bogging out when the throttle is applied, that is normally caused by fouled high speed jets which are fixed..... normally located horizontally in the center bottom portion of the float chambers, way in back of the drain screws.
 

zenwriter

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No, sorry, I didn't describe the issue well.

Engine runs fine at all RPMs, except when put in the lowest possible forward speed (the detent in the throttle above neutral). As when slow trolling or coming into the slip at slowest speed. RPM is about 600 or slightly less and just kind of slows and stalls. If I give it gas as it's stalling there a little hesitation and it lurches forward as it catches.
 

ondarvr

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You have no adjustments, the normal issue is either RPMs are too low at idle, or dirty low speed jets.
 

oldboat1

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Apr 3, 2002
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Don't know where your idle adjustment is (throttle), but think you might be idling a little low. May only need to bump it one or two hundred rpms, warmed up and in gear.
 

zenwriter

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Thanks, sounds about right. My question is, could I optimize low-speed RPMs using Joe Reeves' carb adjustment procedure? (see below): If so, do I do each carb completely before moving to next, or open all 1.5 turns and then do each one?

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

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.

Note: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.

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.
 

Chris1956

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Mar 25, 2004
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Zen, You need to look up the initial setting for the carb idle mixture setting, in a factory service manual. For example, on a '98 90HP V4 motor (60*), the setting is 5-3/4 turns open. Other V4 and V6 models of the same year have different initial settings.

I am not sure what motor you have . You will want to get it correct.
 

Faztbullet

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Mar 2, 2008
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You cannot use Joe's method on this model.....has to be in water,untethered, in gear to adjust correctly.
 

Joe Reeves

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You cannot use Joe's method on this model.....has to be in water,untethered, in gear to adjust correctly.

In agreement with Fazbullet and the other members..... Ignore/discard my carburetor adjustment procedure as it does not pertain to your engine.
 

zenwriter

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Nov 1, 2010
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Thank you all, I found it on page 2-42 of my service manual: (J90VLSSE Year 2000): Initial setting is 5 3/4 turns out for slow-speed needle valve, then adjust in and out when boat is idling on the water in forward gear.
 

ondarvr

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Apr 6, 2005
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I thought the adjustments went away in 98' when all motors needed to meet EPA emissions, but not so on these I guess.
 
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