Piston rings

[Mike 23]

I can't say how much I learn from this forum. Thank you guys!

I am in process of rebuilding my engine. I had low comp. and open reed and leaking lower unit and few other problems that i am trying to deal with. So far I removed all three pistons by pushing them out from the back through the reeds. Thank you Frank! The first piston (top one ) is very dry which i gathered cause of lean gas. Am i right?

Secondly how do you free the ring?. I cleaned them and soaked them in DW40 but no success. Any suggestions?

Thank you!

 

[Frank Acampora]

Re: Piston rings

Some of them are so carboned in that they are almost welded. You need to take your time. Work something under one edge of the gap and carefully and slowly work your way around. You need to keep wiggling the ring as you go. Hurry too much or get ham-handed and the ring will snap. This is assuming the piston is not scored and re-usable. If the piston shows signs of scoring with the aluminum tracks running through the rings, forget about it. You will break the rings before they come out.

One hint which was given to me and which I have not yet tried (I have not yet needed to--eventually I will): Spray the rings with oven cleaner. If you try this be extremely careful! Oven cleaner is highly caustic! You will need to be fully clothed (no exposed skin) and use goggles and gloves. For this reason I do not recommend it. If you should try it, let us know the results.

A lot of the guys here recommend Sea Foam to decarbon a running engine. Try it full strength on the rings--couldn't hurt.

 

[Mike 23]

Re: Piston rings

Frank, as you said the rings were so badly carboned that i couldn't get under it or grab. I used oven cleaner didn't help much. i think because this was an extreme case. I ended up paying $45 to remove them. Now i have almost all the parts, 67 pieces to be exact.

I read almost all the postings that had anything to do with powerhead as well as lower unit. I am using my old pistons with new rings. I am going to hone the cylinders and using transmission fluid instead of soapy water. Is that okay?

one other big oops I didn't pay attention to the piston's position when i was removing them. They came our so easy that i forgot to take a picture. Pistons are convex crown type. Could anyone tell me how they should go back in? remind you i push the pistons out through reed opening.

Thank you!

if everything goes well i might be able to put this baby back in the water by Monday!!

 

[Bigprairie1]

Re: Piston rings

...let me know if this link takes:

http://victoria.kijiji.ca/c-cars-ve...rysler-Piston-and-Rings-Kit-W0QQAdIdZ21377709


Basically it is a guy locally who is selling brand new still in the box piston sets (pistons, rings, wrist pins and clips) for I think about $65eac. (Can$). However if you bought all (3) in U.S bucks you could probably get them very cheap.
Anywhooooo, just a thought.
...I even thought about picking them up as spares.

 

[Frank Acampora]

Re: Piston rings

If you are honing with the crank in the block, be sure to pack the bottom of the cylinders with rags or paper towels to keep grit from getting to the bearings. After honing, be sure to clean out ALL residue before installing the pistons. Even better, if the engine is off the boat, turn it so the cylinders face down and most of the crud will run out onto the ground. But again, be meticulous in your cleaning.

I assume you are honing just to break the glaze and not to clean up scoring. Be aware that the factory only allows .002 wear on the cylinders so if you get ham-handed with the hone you may very well exceed that- Its not a death sentence for the engine but you will not get top performance. The engine may already be out of tolerance due to normal wear and it will have run very nicely.I have had a couple I rebuilt that were .005 out and ran well until they melted a piston and it needed replacement. If you are just breaking the glaze, use a fine stone in the hone.

 

[Mike 23]

Re: Piston rings 85hp 1986

Re: Piston rings 85hp 1986

Big Prairie - thank you for the listing they are rally cheap, but i already got the rings.

Frank - yes i am honing with the crank in the block. I am going to pack the bottom with rags. It looks like bottom cylinder will be a challenge as 1/3 is behine the edge of the lower cover body.
If i can't get to it, is it a lot of work to lift the power head? I already droped the leg.

Thank you!

 

[Frank Acampora]

Re: Piston rings

You don't need to remove the block. If you unbolt the lower cover, and a few associated parts, It will not come off all the way, but you can lift it and tilt enough to clear the bottom cylinder.
By the way: When you hone, run the hone rather slowly and constantly move it in and out at a rate that will give a 60 degree cross hatch pattern. This is not critical, but that pattern, according to generally accepted procedures, is the best to allow the rings to seat.

 

[Daphne444]

Re: Piston rings

I'm curious how hard is it for a novice to just hone the cylinder to break the glaze. It looks like I'm going to have to pull the head to take a look at a low compression cylinder and if the cylinder walls look OK I would rather not pull the entire block from the outboard.

Would this be something that a novice could do, or should it be left to the professionals?

Thanks

 

[Frank Acampora]

Re: Piston rings

Not really difficult at all. You can buy a hone at Sears--maybe 20 bucks? Replacement stones are available also. You need to develop a feel for how fast to run the drill and how fast to move the hone in and out to get the proper cross-hatching. But to just break glaze, you are not really removing metal.
Now, if the cylinder is scored even lightly, you can not do it by hand. It is necessary to have a pro do it because you need to remove metal evenly otherwise you will egg shape and/or taper the bores. The engine will run, but not at peak performance.

BTW: a lightly scored cylinder MAY deliver adequate compression so a light honing MAY suffice. But----If in doubt, send it out.

 

[Nate3172]

Re: Piston rings

Frank is right, don't get crazy with the hone. Another easy way for a person that has never honed a cylinder before to get good cross hatch is to use a berry brush type hone or dingle ball hone as they are often referred to. These work excellent in comparison to the straght three fingered stone style. They can be purchased from Napa auto parts stores.

 

[Mike 23]

Re: Piston rings

Does anyone know the ring number for 1986 85 L drive 856X6L? I got the part number from Sierra - 18-39010 and it doesn't match (at least one of the rings). One is flat but the other one is grooved in one side. It looks like i need to send them back to iboat.

Thank you!

 

[newbie4life]

Re: Piston rings

We used this site religiously to learn about anything we needed to know while rebuilding this engine.

But for good parts diagrams, we went here:

http://www.mercruiserparts.com/Show...&inbr=1226&bnbr=9&bdesc=CRANKSHAFT+AND+PISTON