How Blue is Too Blue? Crankshaft bluing - Evinrude 140 Looper.

[Chinewalker]

I tore down a blown 140 Looper this weekend, c. 1988. It had badly scuffed three pistons, due to an overheat. The overheat was caused by the bracket that the water tube fits into coming loose from the adapter plate by the exhaust tuner. All three bolts were just gone with the bracket hanging loose!

Anyway, pondering what to do with the powerhead - got the crankshaft out and it has some pretty dark bluing at the upper main bearing area. How blue is too blue? Is the crank ready for the scrap bin or is it still usable?

 

[Scott Danforth]

for the material to stay blue like that, it got way too hot and probably annealed the crankshaft.

blue would indicate the material got over 500C and the annealing point is about 340C

 

[F_R]

Guys, just thinking out out here, what would you say to having it hardness tested?

 

[Joe Reeves]

I see the discoloration but no ridges, wear, whatever. The bearing is junk of course... but... the crank? Could be just surface blue. I'd try some wet/dry 600 with a little mineral spirits just to see how much time it takes to obtain the mirror finish.... UNLESS all throws and the bottom main follows suit.

 

[Chinewalker]

No Title

The rod journals don't look too bad. I may try polishing it to see how deep it goes. If there's any question, in the scrap pile it goes...

 

[Scott Danforth]

old cranks make good wall art

 

[racerone]

I always polish the journals with a nice crosshatch pattern.-----There is nothing wrong with that crankshaft !!

 

[Faztbullet]

I myself would not install it in any customer motor...

 

[boobie]

I'd polish it up and use it.

 

[ondarvr]

I never put any questionable parts back in a motor, the cost and hassle of it failing, then needing to rebuild it "again" just isn't worth it.

 

[HighTrim]

My 2 cents.....

If it were my own motor, I would try to polish it out and use it.

If it were someone else's motor, I would recommend they find another crank, or warn of possible failure. You know that if anything ever happens, you will hear nothing but squawking and you will be the devil. Not worth the trouble!@

 

[racerone]

A quick wipe with 220 grit and the " blue " is gone.----If it truly got really hot there would be much more damage to it.

 

[jimmbo]

You don't show the center bearing journal. Its condition?

 

[racerone]

Post some pictures after polishing !