trainfan1 wrote:

AMD Rules wrote:

Hello,

I have a 40HP '69 Evinrude with Electric shift, pushing a 1980 16ft
Munro boat. Having just acquired this combo I am a still getting
familiar with the unique behavior it exhibits. The boat was in
storage for the past three years.

When first tried, the cylinders were misfiring yet it seemed to run
reasonably well. I changed the plugs, points, the consensers, and one
of the coils. It then ran fantastic.... until now. Yesterday
afternoon I was left stranded after the key sheared on the flywheel.
Moments before the engine stopped, it seemed to hesitate briefly then
rev up as if the prop had come out of the water. Did this twice, then
under reduced throttle it simply stopped mid-stroke. I was towed back
to safety by a friend. Lucky for me I had my cell phone. I was
paddling distance to shore, but an offshore wind on lake Huron would
have provided me with a workout to say the least.

I'm assuming that the sheared flywheel was a result of my recent
servicing of the ignition system, and improper seating of the taper.
I have since lapped both of the tapers, and appear to have a good fit.
Awaiting a replacement key.

Is the ONLY reason a flwheel key shears due to improper shaft & nut
fitment? Perhaps this is a dumb question, but I was wondering if
there could be any other reasons for the key to shear.

I'm actually happy, because my initial thought while bobbing up and
down in the waves like a piece of driftwood was that the lower end
(electric shift) had failed. A sheared key is a relatively minor
nuisance.

Thoughts?


Torque to specs... then retorque after an hour running.

The key could shear with a hard prop strike, too.

The 40's were not high revving engines, over revving may set up some
weird harmonics / out of balance issues.

Rob

Whoops.... I didn't mean to imply that the prop came out of the
water...just that is 'sounded like it'. I believe it over-revved a bit
only after the key sheared. I will re-torque ater installation per your
kind advice. Thanks for the quick reply.