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1974 Johnson 25hp manual start

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generalbill55

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"I have a 1974 25hp manual sta

"I have a 1974 25hp manual start Johnson. I have replaced the fuel pump and fuel lines. It ran fair the first time I used it and started fairly easy. I decided to replace the vacum line and another rubber line that runs from the bottom of the engine to a fitting behind the carb., (I think it recirculates the fuel), now I can't get it to start. It tries to run, then it backfires and quits. I checked the plugs and they were wet with fuel. This motor sat several years without being started. Is this a fuel problem or ignition problem? I appreciate any help, thanks Bill"
 
You need to check whether your

You need to check whether your ignition can fire a gap of 1/4" or better-----nothing less will do for a good system.This is step #1 for you to try.
 
"Sitting several years, the ca

"Sitting several years, the carburetor will need cleaning and rebuilding BUT follow ikia's advice first and get the ignition as it should be."
 
"A little help in that departm

"A little help in that department. Make sure that the high speed jet located in the bottom center of the float chamber is clean, also clean that small thin tube leading from the bottom nozzle section of the upper body to the top slow speed passageway.

(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 1: 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.

Note 2: If the engine should be a three (3) cylinder engine with three (3) carburetors, start the adjustment sequence with the center carburetor.

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.

When time permits, visit my eBay store at: http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store

(Carburetor Float Setting)
(J. Reeves)

With the carburetor body held upside down, the float being viewed from the side, adjust the float so that the free end of the float (the end opposite the hinge pin) is ever so slightly higher (just ever so slightly off level) than the other end. And when viewed from the end, make sure it is not cocked.

When time permits, visit my store at: http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store"
 
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