Page 133 - MercMarForc_Catalog_Flipbook

Mercury / Mariner / Force

PISTON DESIGNS

There are four basic piston designs used in Mercury / Mariner / Force engines;
DFI, Crossflow, Loopcharged and Four-Stroke.

DFI Crossflow Loopcharged Four-Stroke

The innovative optimax The oldest design, and the In 1976 Mercury / Mariner / Four-stroke / four-cycle
direct injection delivers the one used on Mercury / Mar- Force introduced V6 engines engines have oil stored
ultimate in efficiency. The iner / Force 35-150 HP with looper pistons. This in the crankcase and is
dome shaped piston head engines from 1970-1990 engine was the 175 HP V6. splashed onto the cylinder
directs the air-fuel charge is the crossflow piston. As A loopcharged engine has walls for piston and ring
to the spark plugs more the air / fuel mixture travels a transfer port cast into the lubrication. The four-stroke
efficiently providing out- through the transfer port and cylinder wall in such a way pistons are equipped with
standing running quality into the cylinder, a deflector, that it will direct the air / fuel oil control rings to scrape
along with excellent reliabil- cast into the top of the piston, mixture towards the combus- excess oil off of the cylinder
ity. Thanks to the two stage directs the air / fuel mixture tion chamber and spark plug walls. Four-stroke pistons
direct injection technology it towards the combustion tip without the need for a are easily identified by a
supplies a constant mix of chamber and spark plug piston deflector. All engines three piece oil control ring
atomized fuel and air to the tip for maximum efficiency. with a flat top or a slight in the bottom ring position.
spark plug thereby lowering All engines with deflectors dome on the top of the The pistons almost always
emissions and enhancing on top of the pistons will be pistons will be loop-charged. have a flat top or a dished
fuel economy. The DFI can crossflow engines. External Loopcharged engines will not top and never have needle
be Identified by splash well inspection of a crossflow have removable transfer port bearings between the wrist
on top of piston. engine will reveal removeable covers on the side of the pin and connecting rod (like
transfer port covers on the cylinders. two-stroke engines).
side of the cylinders.

Piston with Dome Top Piston with Piston with Piston with Flat Top & Oil-ring
and Splash Well Deflector Top Flat Top in the Bottom Position

Standard Removeable Non-Removeable 3 Rings w/ Oil Control Ring
Ring Set Transfer Port Cover Transfer Port Cover in Bottom Position

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