1978 Evinrude 20hp lower unit issues

[Vintage Boat Guy]

I recently purchased a 1978 Evinrude 20hp and the lower unit was tight. I took it apart to discover that the pinion gear was destroyed. What causes this? Also wondering what kind of wear is tolerable for the rest of the gear case parts

 

[flyingscott]

The pinion gear usually gets destroyed because the bearing above it goes bad. Sometimes it takes out the forward and reverse gear with it check those carefully. It can also be wrecked by a bad clutch dog when it starts jumping out of gear.

 

[Vintage Boat Guy]

Clutch dog looks great, must be that bearing then

 

[AlTn]

was there a thrust washer in place on the pinion?...btw....are you certain this is a '78 model 20 hp.?

 

[Chinewalker]

That bearing usually goes bad because the unit was run with water inside it at some point.

 

[hardwater fisherman]

was there a thrust washer in place on the pinion?...btw....are you certain this is a '78 model 20 hp.?

There was a 20hp made and sold in 1978 in Canada. My neighbor has a 76 and a 78. If you look under Evinrude recreational outboards 1913-1979 you will see they made 4 models of the 20hp in 1978.

 

[Vintage Boat Guy]

I figured it out, its a splined shaft and the prop mush have hit something which prevented it from moving causing the pinion to burn against the gears. By looking at the rest of the parts, this is the most reasonable explanation.