TOPIC: Danger!!! Check your Sierra Marine piston rings

I've been having some serious difficulty getting the correct pistons rings from Sierra Marine lately.
I am not sure if it is 'industry wide', since as you might know,...I focus primarily on the inline-6 Mercs.
I discovered this fall that the Sierra Marine ring packs identified as 18-3902 for a standard bore 99ci inline-6 Merc are totally not safe to install.
Granted,...If you get a set of these rings that are bright steel in color with the white coating on the wear surface,...They are probably okay to use.
BUT,...If you get a set of their most recent batch, that are dark steel in color, you will find that when installed in a STD (standard 2.875") bore,...They will only provide .005" max of ring gap.
Mercury Marine specs call for .018"-.025" of end gap, so if you installed these dark rings, once the Merc has warmed up, the ring gap will vanish and the catostrophic carnage will begin.
My sourse told me that the response they got from Sierra Marine was,..." Well just tell them to trim the ends of the rings back."
What a retarded thing to state. Sierra Marine has apparently acknowledged they do have a new vendor they are using for pistons rings.
OMG!!! What a retarded comment for a pencil pusher to make. GAG!!!
If any of you have a connection to the right guy at Sierra marine,...Please share this info and see if you can get this resolved.
In the mean time,...I strongly recommend using merc Marine rings # 39-78816A12 for STD 99ci Mercs & STD 800 & 850 4 cyl Mercs.
Doc Frankenmerc

Sure glad you are on top of this Thom. It sure does sound like something some exec. would say. I guess they really must want to loss money in the long run. Skip.

Unfortunately with outsourcing this is the way of the world these days. Quality has taken a backseat to cost and profits and there is not a lot we can do about it except boycott them, but where do we turn? Merc does not support the classic engines like the inlines anymore so we have to turn to the aftermarket or used, and hope for the best. Just the sign of the times I guess. I was talking with an automotive engineer a while back and I asked him why new cars were packed with so much electronic gadgets like BMW's i drive that nobody could fix and was totally unnecessary. He told me that auto manufactures are fighting for their lives right now to sell cars to the younger market, as most of them don't want to have anything to do with driving at all. Their solution is to make them look and act like Ipads to lure them into the drivers seat, and get the money out of their wallets. So we all suffer for it when these high tech rolling computers go blooey and cannot be fixed by mere mortals, or the cost outstrips the value. Wow. The marine industry is no different, they are in the market to sell new engines, not to fix old stuff that pollutes too much so guess who gets top billing? Better start hoarding parts while we still can.

Thanks for the heads up Doc. I am going to print this out and put it with the 2 Mercs I have yet to redo.

Morris_wil

Heard some folks talk about SIERRA parts at a motor swap meet.The general agreement was that the pennies saved are just not worth it.

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Agreed those " pencil pushers " know very little about fine machinery and stuff that needs to stand up to " full throttle only " use.

Well as any know, doing rings you always check end gap. But agree that crap getting now simple aint what ya think. Doc, if ya don't, ya better get a gap grinder, as looks like in the future will get put to use!

Sadly in this case,...Trimming the ends of these rings is not a solution because the relaxed O.D. of these faulty sized rings simply will not expand enough to put the needed pressure 'outward' onto the cylinder walls.
Use of .015 OS rings that get their ends trimmed correctly will work if correct STD rings aren't 'in hand'.
In a 'good block' with no taper wear, the end gap can actually be trimmed closer to .018" end gap to gain a wee bit of compression, but with today's gasoline quality it just isn't worth the effort unless you are going for the winner's circle and have access to 100LL (airplane gasoline)
Beware too (IMHO) that adding over-the-counter 'octane boosters' can actually result in piston melt-downs because of the lack of necessary lead additives to keep the pistons happy.
Doc

Doc, great info but dont understand this line? "[Sadly in this case,...Trimming the ends of these rings is not a solution because the relaxed O.D. of these faulty sized rings simply will not expand enough to put the needed pressure 'outward' onto the cylinder walls.
]" I can't understand how removing about .015 from the ring end gap will have an affect on sealing pressure? Please explain, I'm an idiot

If you have the correct ring laying on the table beside the wrong ring and you can visibly see that the wrong ring has a smaller O.D. at rest, and that the end gap at rest of the wrong ring is visibly shorter than that of the correct ring, it would be logical to me that the wrong ring would not have the ability to expand outward against the cylinder wall as well as the correct ring.
Consequently, even if the end of the wrong ring was trimmed back to provide adequate end gap, this ring would be more likely to allow the skirts of its piston to make undesired contact with its cylinder wall.
This just my humble opinion.
If someone has more insight on this thought, please post.
There are a LOT of very experienced folks on this forum, that in many cases know way more than I do.
Doc Frankenmerc Keepin' Mercs Alive Since 1965

well having built more than a few race car engines.. you should never just drop a ring in an engine and hope for the best without checking ring gap.. i know most people dont have the tool to file rings.. but i would rather have a tight ring and fit it to specs. than have a loose ring that is junk.. always check ring gap...

now if your pistons have pins in them to locate the rings this can make this a big problem. i know some pistons have pins and they are notched at the ends of the rings to fit around the pin....not sure about mercurys.. my 1960 johnson im rebuilding right now does..

Doc, I understand what you mean here."relaxed OD size" ..basic smaller than the correct ring.
Bill, its not that gapping the smaller ring would hurt anything, but its as the wrong ring in relaxed state is not as large as correct ring, a bit bigger and more in "tension", against the walls. Had I know this yesterday when I was at the Docs, I would have brought my Mics, and do a size comparison.

And on the "pinning" its for sure a "2 stroke thing", so the rings end gap does not rotate around to where a open intake or exhaust port is, as too easy to catch the port, and well, there goes the motor.

Heres a good explanation "how a ring works" Correct ring gaping, and sealing is the heart of any engine build! Guys hard to understand, but self explanatory.

Thanks for clearing that up for me, was a bit confused. Didn't doubt what you said Thom, just the way I read it I guess.

A ring note about my 140 Corvair. I rebuilt a 140 and used Chrome rings in honed but not turned barrels and took about 3 months to stop smoking, after about the first two weeks got stopped by a cop and I told him why it was smoking and said fine, move on, Cool. Then the trans went dead ;(

In order to determine the ring pressure you would have the measure the tension.

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No one can tell here how much tension a ring will have by " looking " at it.

Im just going to throw out a few thoughts here.
Can,t judge those rings without measuring them with a mic.
I agree, you cannot see "tension" in a ring.
Tension is not important, heat and combustion pressure seat the rings against the cyl wall.
Cant show two rings in two cyl and make an informed decision, one cyl could be larger in bore.
ring gap should be measured where the rings run in the cyl, not at the opening of the sleeve.
Any brand of ring could exhibit the same scenario.
99.99% of the time I agree with Thom!
Good thing Thom checked the end gap!

Back in the 70's I bought an engine rebuild kit from JCPenny's. The pistons would not fit into the cylinders with the rings installed. A ring alone in the cylinder would overlap, my best guess was they where for a bored out cylinder. JCP would not exchange or refund the kit. I ended up trimming all the rings to get the proper gap when installed. The motor smoked from day one and in a couple thousand miles it was really bad. The engine was also loosing power from reduced compression. Later I was told that you can get away with trimming rings a couple thousand's. The more you trim the more out-of-round the rings become when installed. Being out-of-round will prevent the seal needed.

"This just my humble opinion.
If someone has more insight on this thought, please post.
There are a LOT of very experienced folks on this forum, that in many cases know way more than I do.
Doc Frankenmerc"

Thanks guys for clarifying and correcting all this.
That is how we all can learn for each others experience.
This is what makes this such a great forum.

Doc F