'85 Force 50HP Sheared Flywheel Key

[roydongi2]

Hello everyone, I am hoping some can help. I inhereted a 15ft Runabout with an '85 50HP Force outboard from a brother-in-law. The first time I took it to a lake the RPM did not sound normal at WOT, and the boat ran slow with 4 people on board. I am a bit of a mechanic but not so familiar with 2-stroke let alone an outboard motor.

I browsed on the web and found a website with blown up parts manual and found that this engine has a set of contacts to trigger the spark plug coils below the flywheel. I purchased a shop manual and found the contact set and plug settings (gap).

Now the problem... I am shearing the woodruff key on the Flywheel, only after a minutes of test run with the engine! I am on the third key... Is this because the flywheel nut is not torqued to specs?

Any help would be highly appreciated.

 

[JB]

Re: '85 Force 50HP Sheared Flywheel Key

Ahoy, Roy.

Welcome to iboats.

Torque on the nut? Could be. Your manual should tell you how much.

Too little torque is probably the most common cause of shearing a replacement key, but there are others.

Wrong key. . .metal too soft or wrong dimensions?

Damaged crank and/or flywheel not allowing the FW to seat completely?

 

[roydongi2]

Re: '85 Force 50HP Sheared Flywheel Key

Thanks JB for the feedback. Much appreciated. I am still waiting for the new FW key to arrive on the mail. But in the meantime I read up on the shop manula again and my problem is leaning towards what you mentioned torque on the nut. I am used to regular car flywheel with several screws and no key.

I have prepared the FW though by lapping it to the cranckshaft. I think I have this lapped pretty well. But will see how it fits when the key arrives.

Thank you once again.

 

[roydongi2]

Re: '85 Force 50HP Sheared Flywheel Key

Got my woodruff key installed it and after all the point gap set, torqued the Flywheel nut to 105 Ft. Lbs... I was able to find a nice FW holding tool from our local Harbor Freight for $10. To anyone interested on this tool it is item #66385 at Harbor Freight. Had to modify this a bit though so that it fits under the FW and in between the stator coils. Works really well! Enough Adds...

After I torquing the FW and checked to make sure all is well, started the engine and it fired right up. Problem though is that the engine tends to rev up a few seconds after I throttle down to idle. Temp is good and I checked the timing with my timing light and seemed fine at 28 BTDC.

I ran the engine with the leg submerged in a trash bin full of water. I let ran for at least 30 min with occassional burst of accellaration. I engaged to forward gear and allowed it to run in idle... All seems fine... I will be taking the boat into our local lake this weekend and hope everything goes well.: