1968 18802M 18 hp Evinrude Crankshaft key & Cam Magneto breaking

[BassAckwards80]

I'm continually breaking the crankshaft key and the cam magneto. I'm getting backfire or something close to it that's causing these two parts to continually break.

Any ideas what could be causing this would be greatly appreciated.

 

[Will Bark]

Are you using the OEM key from a dealer or one from hardware store; are you torqueing the flywheel nut down to 105 foot pounds or what the manual says? The gurus say to only use a OEM key and torque to specs. They should chime in later with more info. Good luck

 

[BassAckwards80]

I had 2 crankshaft keys and 2 cam magneto's. What I originally thought was a fuel related issue ended up being a sheared key. I change it out and the backfire from the motor just breaks it right off. It's also breaking the cam's in half. I've never had this happen before. So I went through 2 sets of these in less than 10 minutes.

The parts I had ordered months ago off of marineengine.com so they were OEM. And the flywheel nut i'm not sure if it was torqued to 105 or not, but it was definitely on tight.

 

[nwcove]

"definitely on tight" does not cut it !! both tapers have to be very clean and dry and the fw nut HAS to be torqued to spec. there is alot of energy stored in a rotating flywheel!

 

[BassAckwards80]

Alright, So put another key and cam on and torqued the flywheel down to 105. Tried starting it and the backfire or kick back broke another set.

What else could be causing this?

 

[nwcove]

is the crankshaft taper beat up, flywheel taper beat up? you may need to find a fw or try lapping the mating surfaces. the key does nothing more than locate the fw properly, the taper is a friction fit and need to be perfect on both the fw and crank.

 

[Daviet]

Silly question, you don't have the plug wires crossed do you?

 

[BassAckwards80]

The bottom side of the flywheel has a little bit of damage to it. Switched it out with a spare I have (Top side damage) and put in another key and cam and she's a GEM again. Fired right up! So I'll order another flywheel.

Thank you all for your help and info