Yamaha - 85 - Pitting on Crank -- Too much or nothing to worry about.

[Havana]

Good evening,

I've been reading the forums for years and need some input.

Cranks - cheap new crank vs OEM used.

I chose OEM used, and bought one with slight pitting on a journal. Its going into a yamaha 85 s stroke. I'll use it for regular boating, nothing too fast. Do you think this little bit of pitting is ok? I thought so because I bought the crank but would like your input. As long as there are no high spots I should be good? Also any ideas on how to level it out? I would love some input.
Thanks guys,

Havana

[CUDA]

Not in my world.

[rgsauger]

Welcome to the forum! Can you post a picture?

[Havana]

Welcome to the forum! Can you post a picture?


513177

rgsauger ... Sorry about that... here it is.

[CI STV]

Yeah, that’s not pitting. More like “gouges”, “pock marks”, etc… looks like something for the junk pile to me.
Unless, of course, you can find someone who knows what they’re doing to weld it up with the right material and machine it to spec again.

[ChrisCarsonMarine]

doorstop

[Havana]

I hit it with some 250,500 and 800 grit and it looks much better. I could probably do a touch more but I think its good.513211
This is for a motor that will have fairly light demands so I'll let you know how it holds up. Thanks for the feedback.

[25two.stroke]

I hit it with some 250,500 and 800 grit and it looks much better. I could probably do a touch more but I think its good.513211
This is for a motor that will have fairly light demands so I'll let you know how it holds up. Thanks for the feedback.

Looks damn good in the pic, I almost wouldn't believe its the same journal. However, if it is and knowing what it was before I'd say its still jacked. No longer round. Fishing style application it may hold up for some hours, but never would fly in one I was assembling.

[ChrisCarsonMarine]

Looks damn good in the pic, I almost wouldn't believe its the same journal. However, if it is and knowing what it was before I'd say its still jacked. No longer round. Fishing style application it may hold up for some hours, but never would fly in one I was assembling.
It's not the same journal,it's the metal underneath the same journal,just sanded down past the chattermarks in the surface of the journal.Aside from most likely not being round,the hard shell surface that was failing is now gone,leaving a much softer inner metal that wont hold up to the wear requirements.This is the reason these cranks aren't reground and fitted with oversized bearings like most automotive cranks that ride on an oil film on insert bearings...
Anyway,Mercury,many years ago published allowable specs for polishing...3 tenths.Not tenths of an inch,or milimeter,but of a thousandth of an inch...around a third of a thousandth,small enough that most folks aren't equipped to measure.
I've relaxed a bit on that,and while race cranks need to be spot-on,I'll polish up to half a thousandth on a fishing motor to achieve a perfect surface.
I'm guessing the OP's crank is 15-20 thou undersize now...occasionally I buy one off the net that has had the same treatment...always measure,Chris

[Havana]

Thanks, I used the shoelace method so it is generally round. It wont fly but for fishing I think it will work. I'll go heavy on the oil and I'll let you know in a year how its going.

[Havana]

I didn't know that about the surface metal versus the internal metal. I'm always learning , thanks for the info. I would also imagine its even tough to get good , new cranks with all the junk floating around from China. High tin content, weak underneath. My plan for this motor is to putt up the river in this one and take my kids fishing, its going on a pontoon. Heavy on the oil, light on the throttle... right?

[H2OPERF]

The crank had spalling... it most likely was rusty at one time. It normally starts as pits from rust at the contact points of the needle bearings and journal then progresses into what you had and gets worse until it slings a rod out the side. Cranks with Some small cleaned up pits that are not all the way across the journal on the back side may last but on the thrust face like yours usually never last. Yours was WAY beyond clean up, it has to look like an egg and it will destroy itself in no time. JMHO