40hp johnson sputters

[boatanchor]

1984 johnson mod.j40ecr s/n 7007832<br />engine at idle sputters and blows gas back out carbs and pops out of exhuast.at mid range to full throotle engine breaks up.<br /><br />so far i changed spark plugs rebuilt carbs and installed new jets.<br />395313 40mx 28 c.j. found this number on carbs are these the correct carbs for this engine?

 

[rickdb1boat]

Re: 40hp johnson sputters

Sounds like it's out of time or you have a broken reed. Remove the carb and check that there is not a broken reed. Also, before you do that, check to make sure the timing base under the flywheel, is moving when you apply throttle. Manual would help greatly... Bottom of page:

 

[boatanchor]

Re: 40hp johnson sputters

thankyou for your help i just ordered the manufactures repair manual<br />took a compression test of cylinders 135 psi<br />removed carbs used a flash light to look at reeds everything looks fine they move freely.<br /><br />on this engine it looks like theres no way to adjust the timming?

 

[rickdb1boat]

Re: 40hp johnson sputters

If it were me, I'd recheck the carbs, being everything else is OK. Never know... What plugs are you using and what gap? Do you have good spark on both plugs? Will it jump 7/16" to block?

 

[boatanchor]

Re: 40hp johnson sputters

UPDATE: changed out leaf assy it stopped spitting fuel back out of carbs and poping out of exhaust.but motor runs like your towing a 400 pound skier just doesnt have full power,throotle plates are open all the way?.<br />checked carbs again foat level ok orifices clean,engine boogs if you use primer botton while under power.<br />replaced fuel pump.<br />replaced cd2 pack.<br />tested coils with ohm meter ok.<br />changed spark plugs tested,they have a good spark.<br />adjusted linkage and timming according to manual.<br />removed fly wheel cleaned sensor and magents tested with ohm meter ok.<br />has 135 psi in both clyinders.<br />dont know what to do next iam about to use a 5 pound hammer on it

 

[G DANE]

Re: 40hp johnson sputters

Check if your timer base moves freely. If it starts to open throttle before advancing ignition it will sneeze, spit and sputter. If it gets up running without ignition timing advanced it will feel like it lost a lot of power. Sometimes old greese can make base stick and hardly move.