Idling Problems? - Try This First
May 29, 2011 6:59 PM | Tagged as Carbon and varnish buildup

Carbon and varnish buildup from today's fuels is much worse than it was a decade ago. Here's how to deal with it.

The old outboard motorboat I bought was, I thought, starting to bite the dust.

In the driveway, with the garden hose pumping water to the lower unit, I startled my quiet neighborhood as the motor roared to life -- then died. Amid the sounds of barking dogs and glaring neighbors, I tried again and again to get the 115 to idle. I couldn't even get it to run at high speed for more than a few seconds before it died. Finally, it was just too embarrassing to continue, and I succumbed to calling my mechanic and explained the problem I was having. He arrived the next evening , but instead of lugging over a toolbox full of hardware, he walked up from his truck carrying only a small aerosol can in his hand.

"Hop in there and crank her over when I say so," he ordered, ignoring my questions about the absence of real tools. In the time it took me to hop in the boat, he had the intake cover off and directed the can's nozzle into the carburetor, and said, "Let 'er rip."

As usual, the outboard jumped to life and began to falter. But by that time, the mechanic had shot several ounces of fluid into the engine. It coughed, but it didn't die as I kept the RPMs up over 2,000. The motor ran long enough to allow him to empty the can's entire 13 ounces into the engine, before it stalled when I tried to back it off some.

As the breeze carried a cloud of dense white smoke into the neighbor's yard, I was about to re-start the engine when he told me to relax for awhile before giving it another try. Twenty minutes later, after running the engine for five minutes or so (which blew more smoke and left a smattering of black ooze on the garage door) the engine was idling nicely.

He submitted me a bill for $9.75 for parts plus a half-hour labor. The old boat was, once again, ready to provide enjoyment on the water.

I was so amazed at how that single can of magic had "fixed" what I was sure was a major problem with the motor, I visited the boat dealership the next day to learn more.

"We go through this stuff like you wouldn't believe," said the certified mechanic. "It's one of the first things we do when an engine comes in with complaints of poor idling. And many times, a can of this will do the trick," he added, tossing me a can of Engine Tune.

Basically, the "tune-up-in-a-can" products offered by companies like SeaFoam, Yamaha and Mercury contain highly concentrated detergents, similar to what's found in high-test gasoline, but much more concentrated.

The detergents are carried in a solvent of aromatic hydrocarbons, and since the solvent is a petroleum distillate itself, both agents actually break down varnish, carbon and other deposits in the combustion chamber. This cleaning action frees-up pistons and rings that have been gummed-up with the carbon deposits left behind by gasoline.

According to one industry spokesman, and backed-up by my own mechanic and several others I've talked to, the problem of carbon buildup from today's fuels is much worse than it was a decade ago, and not getting any better.

It's more important now than ever to use these cleaners regularly according to my marine technician at the marina where I have my boat serviced. If you're using 87 octane, leaded or unleaded, no matter where you get it or what brand it is, you're layering on the deposits each time to run your outboard. It isn't much better with higher octane either.

Look at all the additives their putting into fuel these days. It just doesn't burn as clean as gas used to. Carbon and other deposit build-up on marine engines wasn't a problem 10 years ago. Now it's major.

The technician explained that the deposits left by the cleaner gasolines of yesteryear were softer, and easier to clean or simply wear off. Now, he said, "it's almost like the stuff is glued to the pistons."

When that happens, the rings clog and don't allow heat to bypass, and the motor won't idle properly. If it gets bad, the rings can crack, scuffing the inside of the cylinder walls, letting pressure bypass them and reducing compression. Eventually, because the heat can't transfer from the piston to the cylinder walls, the piston expands and grinds to a halt in the cylinder. Things tend to shut down fast when that happens.

The “tune-up-in-a-can” products work much like oven cleaner. You apply the cleaner and heat the surface to be cleaned, allowing both the heat and the chemicals to the job. That's why manufacturers recommend letting their cleaners sit inside a warm engine for 15 minutes to a half hour before running the engine for the final clean-out.

Not only are there more carbon and other deposits left over after running modern-day fuels, but the deposits are tougher to clean off due to two factors.

First of all, outboards today are asked to work harder, perform better, yet be smaller and lighter that previous models. As a result, they run hotter. Second, a gallon of modern fuel may contain up to 15 percent chemical additives to reduce emissions.

Combine the extra heat with the extra chemicals and the carbon deposits left behind can practically bond to the cylinder wall. And because carbon attracts carbon, a snowball effect is created; once you get a layer on, it attracts more carbon faster than did the clean surface.

Manufacturers advise that boaters use a can of their product every 50 hours, or at least as part of annual spring maintenance. My local marine mechanic agrees. Even if the cleansing doesn't solve the problem, the technician has a clean combustion chamber to inspect for other trouble.

The products are simple to use, and may be used in both 2- and 4-cycle engines. With the engine running at operating temperature (make sure water is pumping through to cool the system), simply spray the tuner directly into the engine's carburetor throat. The engine should continue to run as you empty the entire can into the engine, during which time you may have to jockey the throttle a little to keep the outboard from stalling. Maintain at least 1,200 RPMs during the spraying process. Once the entire can is empty, turn the engine off for 20 to 30 minutes to allow the chemical cleaners to do their work. Then start the engine as usual, and run at half throttle for three to five minutes.

There will be a lot of smoke, either white or white with a bluish cast, as the engine's running with the tune-up going into its system, so make sure the area you choose is well ventilated.

If the idle problem is carburetor-related, you will need to use a product that is introduced into the gas system. Fuel for idling and low RPM operation flows through very tiny orifices. If these orifices have narrowed, idling will be effected similar to narrowing of the arteries to your heart. If they aren’t clogged, the cleaners in the gas will be able to get through the inside of the carburetor and through these orifices. In many cases, this will open these openings back to normal. If they are clogged completely, the chemical can’t get through and your next step is a carburetor rebuild, a much more costly endeavor.

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