1970 evinrude 85hp crankshaft thread repair

Andy in NY

Commander
Joined
Oct 25, 2007
Messages
2,109
Hey guys, been a while since ive been on here! Anyways, i havent touched my boat in a year and a half now after my little mishap at the end of the 2011 season. The flywheel nut backed off, making the flywheel bounce around.

I have 2 problems:

1) the the key that holds the flywheel sheared, and I dont know how to get whats left out of there.

2) the threads on the crankshaft are damaged.

20130518_132746.jpg



are these threads too damaged? If they arent, how do i repair them?

if they are, i would imagine the crank is pretty hard to replace. any ideas?
 

Joe Reeves

Supreme Mariner
Joined
Feb 24, 2002
Messages
13,262
Re: 1970 evinrude 85hp crankshaft thread repair

I've always used a sharp pointed center punch to remove sheared keys.

If a new nut will screw on and off those threads, they should be okay. Try one. Be absolutely sure to clean up the tapers of the crankshaft and flywheel before installing a new one.... and purchase the proper part numbered key, NOT one from a hardware store that you think might work (it won't!).

The key must be installed so that it is straight up and down with the engine (pictured below), NOT aligned with the crankshaft taper.

The flywheel nut must absolutely be torqued to 105 foot pounds. Anything less... it will shear!
CS-FW_Key_Align.jpg
 

boobie

Supreme Mariner
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Nov 5, 2009
Messages
20,826
Re: 1970 evinrude 85hp crankshaft thread repair

I don't know the size of the threads off hand but you may find a thread chaser in a local parts house or take it to a machine shop to clean up the threads..
 

Andy in NY

Commander
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Oct 25, 2007
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2,109
Re: 1970 evinrude 85hp crankshaft thread repair

should i be replacing the nut with another aluminum one?
 

multimech

Petty Officer 1st Class
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Apr 26, 2012
Messages
386
Re: 1970 evinrude 85hp crankshaft thread repair

Make sure the taper is in good shape. That is what holds the flywheel on. The key only aligns the flywheel. Make sure when you put it back on the taper in the flywheel and on the shaft are dry and in good repair. DONT USE GREASE. Either file the threads on the crank or use a thread chaser. Torque to spec.
 

Joe Reeves

Supreme Mariner
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Feb 24, 2002
Messages
13,262
Re: 1970 evinrude 85hp crankshaft thread repair

should i be replacing the nut with another aluminum one?

Aluminum??? The nut is steel.

If you have an aluminum nut, replace it with the proper nut available at your dealership. Nut part number 314209. It would be a good idea to replace it anyway if it's even slightly damaged.
 

Andy in NY

Commander
Joined
Oct 25, 2007
Messages
2,109
Hey guys, so here I am 2 years later. I had been so busy that I hadnt even touched or so much as looked at the boat. i got it moved to the driveway today where its more accessable. I got the shear key out, and am ready to start checking the threads. Then it hit me: WHERE IS THE FLYWHEEL?????? Its no where to be found! Im hunting ebay right now for a new one.

Once I know it will still run, I have to rehab the boat again because it sat outside for 3 1/2 years uncovered.
 
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