40 Johnson problems

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Bomberdad

Cadet
Joined
Jul 19, 2009
Messages
6
While out and starting to come in my 40 HP Johnson 2 cyl ran for 5-10 seconds and died...several attempts..had to get towed.
We cleaned carburetor and after several attempts to keep it running, it finally ran but backfired and smoked...new gas, new oil for the injection system...still runs rough and backfires/misses...any clues? we're thinking timing and or power pack...Thanks...FT NJ
 
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Bomberdad

Cadet
Joined
Jul 19, 2009
Messages
6
Re: 40 Johnson problems

new fuel pump/mixer installed recently,,,but ran well after installation (5-6 trips)
 
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petryshyn

Commander
Joined
Oct 3, 2001
Messages
2,851
Re: 40 Johnson problems

Backfires are usually caused by lean mixtures, timing issues, carboned up cylinder, incorrect plugs or problem reeds.

have you tried assisting the fuel system by squeezing the primer bulb?
have you checked for spark quality on each cylinder?
 
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tx1961whaler

Vice Admiral
Joined
May 31, 2008
Messages
5,197
Re: 40 Johnson problems

Check for a sheared flywheel key.
If it turns out to be sheared, replace with the real Johnson/Evinrude one, not a Home Depot variety and carefully torque the flywheel downto the prescribed ft-lbs.
 
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wilde1j

Vice Admiral
Joined
Apr 15, 2002
Messages
5,964
Re: 40 Johnson problems

Backfires out exhaust are caused by incorrect timing ... tx has the right idea. Also, check coil wires go to right cylinders.
 
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coolguy147

Commander
Joined
Jul 14, 2008
Messages
2,817
Re: 40 Johnson problems

make sure ur spark plug wires were on the right cylinder

i dont believe it will run if timing was off mainly cause its a 2 cylinder motor 180 different on each cylinder.

check carb clean it up nice and good get new float and rebuild kit
 
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Bomberdad

Cadet
Joined
Jul 19, 2009
Messages
6
Re: 40 Johnson problems

Thanks all for your replies...will take one at a time! Keep em' comin though!!
 
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