1979 Johnson 55HP Flywheel turns loose

[suraj]

Hi,<br />could anyone explain why the small key that holds the flywheel breaks? i have just broken the 4th one now. how can i fix this?<br />i have 1979 Johnson 55HP (55ETL79C)<br />thanks

 

[R.Johnson]

Re: 1979 Johnson 55HP Flywheel turns loose

After 4 keys, the key-way in both the flywheel hub, and crankshaft taper must be damaged. First cut away any burr's with a fine cut file. Get some valve grinding compound in both medium, and fine grit. Carefully lap the two tapers back into agreement, and clean away all traces of grit. Install a new key, and torque down to 105 Ft.Lbs.

 

[WillyBWright]

Re: 1979 Johnson 55HP Flywheel turns loose

If that don't work, red loctite everything. Threads, taper, key. I had that happen to the same model but a few years older. The tapers on both the crankshaft and flywheel were badly marred from the sheared key. The key really does little to keep the flywheel in place. It's more for indexing purposes. 99% of what holds that flywheel in place is the pressure on the taper. If enough metal is gone so that some of the surface area won't contact the other side, then your clamping capability is greatly reduced. Pressure (torque) alone might not be sufficient anymore. The last resort was to red loctite the flywheel on and the motor ran fine for years after that. Hopefully you'll never have to take the flywheel off again. That would be difficult.

 

[suraj]

Re: 1979 Johnson 55HP Flywheel turns loose

thanks johnson and willy,<br />i will try this weekend and let you know the results. amazingly both the flywheel hub, and crankshaft taper are in very good condition. after i run the engine for 10-15 minutes its starts and coughs and dies and thats when the key breaks. <br />thanks for the advice once again.

 

[llfish]

Re: 1979 Johnson 55HP Flywheel turns loose

Make sure that you are torqueing the flywheel bolts down (105 lbs) an educated guess will not work.

 

[BoatBuoy]

Re: 1979 Johnson 55HP Flywheel turns loose

Years ago, I needed a key and got some key stock from a hardware store. As it turned out, this material was not hardened and sheared repeatedly. BTW, this wasn't an outboard.

 

[rodbolt]

Re: 1979 Johnson 55HP Flywheel turns loose

hello<br /> like RJohnson says<br /> you must lap the flywheel tapers. to check the fit when your done wipe everything of with acetone and place 3 pencil marks down the crank taper. set the flywheel in place and while holing the crankshft still rotate the flywheel 90*. if it removes the pencil marks your ready to reclean and install the flywheel with a new key and a new locknut. use the proper torque specs. then clean the carbs well or more coughing will shear another key. that cough is actually a fire below the piston as its traveling down. the reeds prevent the pressure from exiting the carb so the pressure actually tries to move the crank in the opposite direction.<br />the flywheel cant change direction that fast. so it shears the key and spins on the taper. but lap it well. someplace on this forum I gave a detailed procedure on lapping the tapers.<br />like you were told. the key only indexis the flywheel to the crank for timing the actual holding is done by the inerference fit of the tapers.<br />you will find if the tapers fit well you will have to use the puller after checking the fit sometimes .

 

[suraj]

Re: 1979 Johnson 55HP Flywheel turns loose

thanks all, <br />i have i followed the instructions and hopefully it runs well. u guys are doing a great job! keep it coming.<br />mariner