Piston and Cylinder Opinion

[riverdog01]

Hi, I'm new to rebuilding outboards but I'm gonna give it a go. I'm rebuilding an 8 hp Evinrude 1985. I'm wondering if the piston that is scuffed can be reused, I can feel the scuff on the piston but it doesn't seem too bad. The cylinders I can't see any damage. (see attached pics)

Thanks in advance for your help and opinions.

 

[Haffiman]

Re: Piston and Cylinder Opinion

Hone/de-glaze the cylinders, change the piston.

 

[riverdog01]

Re: Piston and Cylinder Opinion

Thanks for your reply.
I'm also wondering if you would reuse the center needle bearings. Part sites say they are obsolete or unavailable ?

Thanks

 

[F_R]

Re: Piston and Cylinder Opinion

Rule of thumb on bearings: If they are perfect, they may be reused. If not perfect, replace them. marineengine.com has one.

 

[Haffiman]

Re: Piston and Cylinder Opinion

As a rule of thumb, I always replaced center (main) bearings. They may still be ok as bearings, but they even have the function of sealing between the crank cases for the different cylinders.

 

[dazk14]

Re: Piston and Cylinder Opinion

Why did you tear it down to begin with?

Have you tried to clean up the piston a bit with crocus cloth. Pictures can be misleading..

If you're looking for a short money rebuild, that piston may be fine and it doesn't need to be perfect.

Run a hone through it, well lubricated, for about 20 seconds total per hole.

Inspect bearings, they may be fine. Verify head/block is flat.

Always new rings, gaskets,seals.

If this was a high horsepower motor, I'd probably be singing a different tune.

 

[riverdog01]

Re: Piston and Cylinder Opinion

Thanks Guys, I believe it was a water pump issue that caused it. It lost it's compression wouldn't start. I have honed the cylinders they seem good. I have new gaskets. I plan on doing the water pump too obviously. Which seals should be replaced ?

Thanks in advance

 

[boobie]

Re: Piston and Cylinder Opinion

Follow Dazks advice. I've done that on a lot on these smaller mtrs and it has worked. The scuffing on the piston doesn't look that bad and you should be able to clean it up. Just sand across the scuffs, not with them.

 

[Pussiwillow]

Check for cylinder head warpage while it's off, if it's warped, check by laying on an old thick mirror as these are generally straight and true or use a straight edge and run a feeler gauge under the center between the 2 cylinders, if warped, I use 400 grit sand paper tapped to a thick old mirror and sand the head down in a figure 8 motion with even pressure, worked many times for, I took .015 off my current motor, got my compression back, good luck!

 

[1946Zephyr]

Re: Piston and Cylinder Opinion

Yea, that scoring doesn't look too bad. If it doesn't affect the rings, then it'll be okay. Myself, I would go ahead and replace it, but it'll work fine, if you clean it up and re-use it.

 

[riverdog01]

Re: Piston and Cylinder Opinion

Thanks guys, great information really appreciate the help. To give you an update I ordered all new liners and needles for the piston, center bearing, crankshaft seal and an exhaust housing that had a broken bolt hole. Got a decent deal online for the piston bearings but the center mains are about the cost of gold when you factor in the shipping and customs to Canada. I think I'll hold off on the piston while I'm waiting for the parts to see if there is a decent auction on one. I guess I'm in this for the challenge now not because this makes fiscal sense. The head looks ok to me with a straight edge on it but not sure I'm doing that correctly (pic attached). I'll have to see if I can find a mirror.

Thanks again.