175 johnson back fire?????

[toocanshan]

i had bought a 175hp johnson 1984 long shaft that i was told ran. this motor can start but runs for only a few seconds and back fires then stalls. it has spark in all six cylinders and i also checked to see if it's getting gas and it is. anyway i was told if the key on the flywheel broke it would throw the timming off which in turn would make it back fire. how do i check the key to see if it's broke?? and do i need to even check the key and\or is there anything else that may cause this?? thanks to all!!




TOOCAN

 

[ondarvr]

Re: 175 johnson back fire?????

To check the flywheel key, get a socket and undue the nut. If the key is sheared the flywheel might lift right off, but you may need to use a puller.

 

[tashasdaddy]

Re: 175 johnson back fire?????

PULLING FLYWHEEL

you need a harmonic balancer puller, you need 3 - #8 harden bolts, that fit the 3 holes in your flywheel. standard hardware store bolts will strip out, causing more problems. loosen the flywheel nut, leaving it on so it protects the thread. thread the bolts in 7/16 of an inch. then tighten the puller, adjust so it has a straight pull. now tighten the puller, rap the center bolt with a hammer, then tighten some more. you may have to let it sit over nite, and repeat in the morning. this is a compression fitting, it will eventually POP!!. do not loose the woodruff key that goes in the groove of the flywheel and the crank shaft. then installing the flywheel, it has to be totally clean, no oil, woodruff key in place. then torque the nut to the specifications for your particular motor. if you do not do this, the woodruff key with shear, and you will be repeating these steps.

 

[toocanshan]

Re: 175 johnson back fire?????

how will i tell ( once i get the fly wheel off) if i have a problem or not. what am i looking for??? thanks guys for all your help

 

[tashasdaddy]

Re: 175 johnson back fire?????

the woodruff key will be in 2 pieces, one in the crankshaft one in the flywheel.

 

[emdsapmgr]

Re: 175 johnson back fire?????

If it's not a sheared key, check the coils. You may have one on the wrong spark plug. They are color coded.