Scientific evidence for decarb

ddaigle

Petty Officer 1st Class
Joined
Feb 9, 2004
Messages
332
This has been bothering me for a while, and I have searched the forum with little result. I read a lot about the wonderful benefits of a decarb but does anyone have any real hard evidence that it is effective? Im talking about before and after engine teardowns- real scientific proof- not my engine seems to run better or a lot of black stuff came out the exhaust. As much as a decarb is promoted on this site, I would like to see some proof. Not trying to start a fight just like to see claims backed up by evidence.. Thanks
 

JB

Honorary Moderator Emeritus
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Mar 25, 2001
Messages
45,907
Re: Scientific evidence for decarb

Never did it to an outboard, but I used to decarb chainsaw engines before preparing them for kart racing. Before and after depends on how clean it was before. Always clean after.

I used water to decarb back in those days, by the way. The oils we used and the mix we used 50 years ago made a lot of carbon in a short time.

Decarbing an outboard is like taking aspirin. If you had a headache aspirin helps, if your engine is carboned up decarbing helps. No problem, no help but no harm.
 

Silvertip

Supreme Mariner
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Sep 22, 2003
Messages
28,670
Re: Scientific evidence for decarb

What kind of evidence do you want? Nobody is going to tear down an engine, take pictures, reassemble the engine, then decarb it and tear it down again so they can take before and after pictures. That's simply rediculous. Proof of effectiveness comes in two ways: 1) Compression and 2) Runability. Any two stroke that has spent a good amount of its life trolling or perhaps serving pontoon duty where it sees lots of low speed operation can experience carbon build up to the point where it loses compression due to the rings becoming stuck. Doing a compression check on those engines usually shows one or more cylinders down on compression and the owner reports hard starting, rough idle, high fuel consumption, etc. As with any repair work, always do the simplest and least expensive things first. If the electrical system shows good spark and the plugs are ok, do a compression check and follow that up with a thorough decarb. There is pretty fair chance compression will return to near normal. As for runability, getting compression back to normal will help that as well. Especially starting and idle performance. Continued use of a product like SeaFoam, Power Tune, and others will reduce the need for decarbing.

I have a two stroke LawnBoy mower that is still dripping black gunk from a decarb. You got -- poor performance was corrected with an enema of SeaFoam.
 

steelespike

Supreme Mariner
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Apr 26, 2002
Messages
19,069
Re: Scientific evidence for decarb

I have no hard evidence but I have seen folks on here with compression way out of specs and when they do a decarb as suggested compression figures return.
That said In close to 60 years of outboard operation I have never had a compression problem nor done any decarb procedure.
But let me make it clear very little trolling and no extended slow speed operation. These motors range from Firestone,Elgin,Elto,Johnson,Evinrude,Gale,Martin,Merc,Goodyear. From 1- 50
hp.1941 to 88.
 

Bob_VT

Moderator & Unofficial iBoats Historian
Staff member
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May 19, 2001
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25,897
Re: Scientific evidence for decarb

It is a fact that the decarb will help a 2 stroke. I brought an older 18hp fastwin back to life with a decarb. I had removed the side cover and I could see the piston rings and they were stuck. I replaced the cover and did the decarb ..... compression returned and the rings were free and clear. I have seen it work first hand.

Mercury and OMC both make/market their own sprays for it.

Your choice weather to do it or not. So.... what would you suggest to do?
 

studlymandingo

Commander
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Mar 22, 2006
Messages
2,716
Re: Scientific evidence for decarb

I gained about 5 psi across the board by running a can of sea foam in a gallon of gas in my 150 HP V-6.​
 

Frank Acampora

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Jan 19, 2007
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12,004
Re: Scientific evidence for decarb

I have never used decarb but I have torn down a number of old engines. A good number of them had the rings so carboned up that they broke when trying to remove and parts of them were just about welded into the ring grooves. Would decarb treatment have helped these engines? Probably-- but I bought them as junkers specifically for salvage purposes and never even tried to run them.
I have also torn down one or two of my engines after a season or two running and found no carbon problems -- all rings nice and free. But I tend to cruise at high to full throttle settings and I don't think this tends to form carbon deposits.
Just remember that we are all human. Everyone on this forum has their own beliefs and biases. Read all posts and make your own decision based on your interpretation of consensus.
 

ddaigle

Petty Officer 1st Class
Joined
Feb 9, 2004
Messages
332
Re: Scientific evidence for decarb

I appreciate all the responses, and I realize everyone has an opinion. But I like to see verifiable facts not opinions. It would seem to me that a manufacturer of one of the decarb products would have done some test engine teardowns to show how great there product actually is. I am always skeptical of any product that cant produce scientific evidence that it really works. As I stated, saying that my engine ran better or picked up a few points in compression, while nice, is not conclusive evidence. The decarb may have cleaned the carbs out somewhat or caused a temporary sealing of cylinder walls or seals. I have rebuilt engines and worked on them all my life so I am quite familiar with their inner workings. Bob VT ,I appreciate your actually looking at the rings. Having said all that I realize that these products probably would not have lasted as long as they have if they didnt do something beneficial. I have been running outboards for 40 years without decarbing, but I might give it a try. Thanks to all
 

phatmanmike

Captain
Joined
Oct 24, 2003
Messages
3,869
Re: Scientific evidence for decarb

don't do it, you have to believe in the force for it to work, and you obviously don't believe in the force. all it will do is gunk up your rings.

JUST KIDDING......
 

LubeDude

Admiral
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Oct 8, 2003
Messages
6,945
Re: Scientific evidence for decarb

I use it and I believe it works, however!

I just rebuilt a 350 HP 327 out of a Corvette that was carboned up so bad that the pistons were hitting the heads. Just for kicks and giggles, I soaked a carboned up valve in seafoam for about a month. It did nothing, absolutly nothing.

I did clean the tops of the pistons with Naptha, [Which is the active ingreadient of Seafoam] and a heavy scuff pad. Worked fine but was labor intensive.

I believe that the combination of heat and the introduction of the Seafoam while running is the ticket.

I no longer buy Seafoam and just use Naptha. I add oil or alcohol as needed for the application.
 

Scaaty

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May 31, 2004
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5,180
Re: Scientific evidence for decarb

I appreciate all the responses, and I realize everyone has an opinion. But I like to see verifiable facts not opinions.

Well, after years of nothing but good TCW in an 88 Force 125 on one of my boats. I did a Seafoam overnighter. Went from 3200 and below falling off plane, to planing at 2500...
Good'nuff?
 

Silvertip

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28,670
Re: Scientific evidence for decarb

The procedure for decarbing an engine includes specific instructions to warm the engine. Introduce SeaFoam. Let it cook. Fire it up and smoke up the neighborhood. Repeat two or three times if necessary.

For those that insist on using Naptha, you should understand that SeaFoam includes a lubricant which Naptha does not. Spraying that through the engine washes the cylinders.
 

Texasmark

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Dec 20, 2005
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14,271
Re: Scientific evidence for decarb

Not scientific, but my experiences. Upon visiting this site, my first reaction to decarbing was that it was a joke. I said so and repudiated most of what I read based upon my ignorance to carbon buildup and the experienced expertise that I was ignoring.......in my stupidity. Got off on the wrong foot with knowledgeable folks first thing.

Carbon to me was what you used to get on top of your pistons and on the combustion side of your head when you used leaded gas. So I figured that since we are using unleaded gas these days, no need for it........forgot that carbon is a key ingredient in all petroleum products.....also forgot about what age does to petroleum products and heat and all.

So I decided to try it (Sea Foam) and my 2 cycle OB of only 3 yrs of age ran (started and idled) a lot better. So I have been using it ever since.

Then I had nothing to do one day so I experimented with some in an old weed eater I had discarded. Remarkable improvement in running, acceleration and especially starting. Made me wonder why I had bought a new one.

So I dug out an old chain saw, 4 cycle lawn mower, rototiller, and 40 year old diesel farm tractor that I thought needed a serious overhaul.....all serious improvements and no doubt it works.

Now would another product work? Surely. As well? Probably. Do I need scientific evidence? No.

Lube Dude mentioned a test he ran and made an assumption about the running engine being a big part of it. In the past mention was made of a blown headgasket in an automobile that cleans up the cylinder getting the water. Obviously placing engine parts in a tub of water get disasterous results. But in an operating engine, water definitely cleans things up. BTDT

So you can continue with your head in the sand (figure of speech) as I initially did or try it and let your results speak for themselves. You have little to loose and potentially a lot to gain.

My 2C

Mark
 

tmcalavy

Rear Admiral
Joined
Aug 29, 2001
Messages
4,005
Re: Scientific evidence for decarb

This ain't science but answer this: Do your teeth and gums function better clean or with a mouth of plaque/crap? Hmmm....
 

studlymandingo

Commander
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Messages
2,716
Wierd Science

Wierd Science

This ain't science but answer this: Do your teeth and gums function better clean or with a mouth of plaque/crap? Hmmm....

Sure makes kissing girls easier with the use of a toothbrush and some floss.:D
 

Texasmark

Supreme Mariner
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Dec 20, 2005
Messages
14,271
Re: Scientific evidence for decarb

Hey guys (last two posts). You are getting personal now. Grin
 

gss036

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Jan 18, 2003
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Re: Scientific evidence for decarb

I just posted in the other, tech problems, etc about wishing I had know what was going on inside of my 4 yr old Husky 359 chain saw. Everything was completely carboned up and I have used "KLOTZ" motorcycles full synthetic oil exclusively in the saw and it has only seen about 3-4 gallons of gas and cut about 8-9 cords of wood and it was totaly trashed w/carbon. The ring was complety frozen in place, I think, had I know this, a good treatment of SEAFOAM may haved revived the saw, albeit temporary. I Had to put a new powerhead on it. Glad it was not an outboard, but still spendy no less, and GUESS WHAT! I threw out my KLOTZ oil and will go buy regular chain saw oil for future use. So much for my confidence in synthetic oil.
 

ziemann

Chief Petty Officer
Joined
Apr 28, 2004
Messages
584
Re: Scientific evidence for decarb

So you used a TCW-3 oil designed for a higher temperature motorcycle engine and really used it on an air cooled engine that needs TCW-2 for lower temperature combustion chambers- AND you blame the synthetic??????

2 very different applications- 2 very different temps of combustion chambers- this is user error.

ENOUGH of the thread hijacking.....
 

gss036

Commander
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Jan 18, 2003
Messages
2,914
Re: Scientific evidence for decarb

Ziemann!!!!!!!
NO HIJACKING here, you need to reread what I posted. I was just making a good case for using SEAFOAM.
IT was not TCW rated oil but KLOTZ Syn motorcycle racing oil designed for high RPM and high temperature air cooled 2 stroke motor cycle racing engines. I sometimes, do not post because of some of "cyncial" replys that some people post.
Really do not mean to rattle your chain, just trying to be friendly.
 
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