back fire

[daniel vinson]

My 225 Johnson out board will not start. Every time I try it back fires out the exhaust directly behind the motor not the prop. I replaced the plugs and wires, but dont know how to check the timing. Really dont know what could be wrong. Need help ASAP!

 

[Benny1963]

Re: back fire

crossed up wireing sheered flywheel key
you can pull your timer base forward and check your timeing .turning it over
your timeing -4 % if your timeing at cranking speed is off ya possibly sheered a key check all your ignition wire carefully you really need oem manual

 

[tashasdaddy]

Re: back fire

99% shear flywheel woodruff key.

 

[kenmyfam]

Re: back fire

Agree with the woodruff key.
Welcome to iboats

 

[tashasdaddy]

Re: 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.

 

[crxess]

Re: back fire

Woah.... Was this a running engine before you started changing plugs and wires?
If it was a running motor(ran fine last use) something probably got crossed up when rewiring plugs. 2 wires crossed will cause a backfire and stop piston from advancing it the cylinders that misfire keeping the engine from starting.
Confirm each wire first, then look to other issues.

If you have to pull the flywheel spray a little PB Blast around the shaft before tightening the puller. it will help to free things up. Be patient flywheels are tough to release.