10hp Evinrude backfire issue

[bfitz]

Got some more info on my motor. It was seized from sitting, the guy I got it from freed it up.

Is it possible that the crank seals were damaged during the process?

I'm specifically referring to the large o ring around the roller bearing on the top and bottom of the crank..the little o rings looked ok.

what holds those bearings in the block so they remain stationary?
Thanks

engine's a 1963 model 10302D

 

[tashasdaddy]

Re: 10hp Evinrude backfire issue

back fire is usually caused by timing, which is cause by a broken flywheel key. if the previous owner removed the flywheel to free it up, and did not torque the flywheel properly, 99% the key has broken and the flywheel, and crank are not aligned properly. you need to pull flywheel. harmonic balancer puller, and #8 hardened bolts to go into flywheel.

 

[bfitz]

Re: 10hp Evinrude backfire issue

Hey, thanks for the help.
I took the flywheel off myself...the key was good.
Points set a .020.

Think it could be a bad condenser? I changed them, but who knows. Any tricky was to test them/

 

[HighTrim]

Re: 10hp Evinrude backfire issue

Backfiring out of the exhaust port is caused by having the ignition system fire a particular cylinder when the exhaust port is open ( ie piston down). This would sound like a shotgun going off..... is this the condition that you're experiencing?

This is usually due to a sheared flywheel key, as mentioned by TD, a flywheel with melted (moved) center sensor magnets if they exist, timer base leads routed incorrectly to the powerpack, or having the leads from the powerpack to the coils reversed to mention a few.

Spitting back, sounding like a mild backfire, indicates a carb slow speed restricted jet..... something causing a lean carburetor scenario. Remove the carburetor face plate. With the engine running and with that coughing condition existing, stick two fingers into the carburetor throats, one carburetor throat at a time. You will be acting as a manual choke of sorts.

If you find an offending carb, the rpms should increase slightly and the cough should stop.

If you can't find anything wrong with the fuel system, consider a possible leaky lower crankshaft seal, admitting air to the lower cylinder and resulting in a lean sneeze of the lower.