"TUNE UP IN A CAN" PRODUCTS
OMC's Engine Tuner and Mercury's equivalent can do a bang up job of cleaning carbon and
oil build up from the piston, piston rings, and cylinder heads of 2 cycle engines.
Depending on your choice of fuel, oil manufacturer, and idling habits, the recommended
application of these cleaners, is at least annually. Those who troll a lot should shorten
the time frame. But don't get carried away and always carefully follow the instructions on
the can . It's very potent stuff and will remove paint and damage some plastic parts if
left on too long. It also can be used as a carb parts cleaner for a carb you had to remove
The problem of carbon build-up from today's fuels is much worse than it
was a decade ago, and not getting any better. Basically, these "tune-up in a
can" products contain highly concentrated detergents, similar to what's found
in today's gasolines.
These tune-up in a can products contain detergents that are carried in a solvent, and
since the solvent is a petroleum distillate, both components actually help 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 the gasoline.
When the rings become clogged, the carbon acts as an insulator that doesn't allow heat to
transfer from the piston to the cylinder wall. If it gets bad enough the rings can
crack, scuffing the inside of the cylinder walls, letting pressure bypass and reducing
compression. Once this process starts, it gets worse quickly. Because the heat can't
transfer from the piston to the cylinder walls, the piston expands and seizes in the
These cleaning products are simple to use and can be used in both 2 and 4-cycle engines.
Tune-up in a can products work much like oven cleaner. You heat the item to be cleaned
then apply the cleaner , allowing both the heat and the chemicals to the job.
Note: Never run an marine engine without
Warm the engine up to normal operating temperature. Try to maintain at least 1,200 RPMs
during the spraying process. If the engine has more than one carb, distribute the fluid
evenly between the carbs. You may have to fiddle with the throttle a little to keep the
motor from stalling. Also, be sure to wipe up any drips or over-spray. If it can remove
carbon, it can remove the paint job from your motor too.
Once you have sprayed the recommended amount into the engine, stall the engine with the
spray and turn the key off. In colder climates put the cowling back on, to keep the engine
warm. Soak for 20 to 30 minutes to allow the chemical cleaners to do their work. Then
start the engine as usual and run five to ten minutes between 1000 to 2500 RPMs. It
is generally best to lake run the engine under load as soon as possible to help remove all
of the cleaner and goop the cleaner loosened up.
Large engines require a whole can of cleaner but very small engines probably only need 1/8
to 1/4 can to do the job. The way to tell is when you are getting a heavy white smoke from
the exhaust, you probably can spray a little more, then let it stall. (My usual rule of
thumb for current model 9,10,15,20,25,30 hp two cylinder outboard motors is a 1/2
can of cleaner, give or take.)
The real trick is to use the product regularly, this holds especially true if you use your
motor for trolling. It really doesn't matter which manufacturers brand, they all seem to
work pretty well.
By the way, OMC makes a special injection-style of its Engine Tuner, which attaches
to a tire-valve type fixture on late model OMC outboards that have a separate electric
fuel primer, instead of a choke. Ask your servicing dealer about it.
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