Mariner 100, Service Manual, Page: 146 / 391

4A-18 90-13645--2 495 POWERHEAD
CYLINDER BORE SIZE
Piston Size Cylinder Block
Finish Hone
Standard Diameter 3.375 in.
(85.725mm)
.015 Oversize 3.390 in.
(86.106mm)
.030 Oversize 3.405 in.
(86.487mm)
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Inspect cylinder bores for scoring (a transfer of
aluminum from piston to cylinder wall). Cylinder
wall scoring usually can be “cleaned up” by honing
or reboring.
When reboring cylinder block, remove hone
frequently and check condition of cylinder walls.
DO NOT hone any more than absolutely
necessary, as hone can remove cylinder wall
material rapidly.
CAUTION
HONING PROCEDURE
Follow hone manufacturer’s recommendations for
use of hone cleaning and lubrication during honing.
IMPORTANT: After honing, bores should be thor-
oughly cleaned with hot water and detergent.
Scrub well with stiff bristle brush and rinse with
hot water. If any abrasive material is allowed to re-
main in the cylinder bore, it will cause a rapid wear
of new piston rings and cylinder bore. After clean-
ing, bores should be swabbed several times with
2 cycle engine oil and a clean cloth. Wipe excess
oil with clean, dry cloth. Cylinders should not be
cleaned with kerosene or gasoline. Clean remain-
der of cylinder block.
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Hone all cylinder walls just enough to de-glaze.
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Measure cylinder bore inside diameter (with an in-
side micrometer) of each cylinder, as shown be-
low. Check for tapered, out-of-round (“egg-
shaped”) and oversize bore.
TOP
CENTER
BOTTOM
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If a cylinder bore is tapered, out-of-round or worn
more than 0.003 in. (0.076mm) from standard
“Cylinder Block Finish Hone” diameter (refer to
chart), it will be necessary to rebore that cylinder(s)
to designated oversize bore and install oversize
piston(s) and piston rings during reassembly.
NOTE: The weight of an oversize piston is approxi-
mately the same as a standard size piston; therefore,
it is not necessary to rebore all cylinders in a block just
because one cylinder requires reboring.
IMPORTANT: Ports must be deburred after hon-
ing.
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After honing and thoroughly cleaning cylinder
bores, apply 2 cycle outboard oil to cylinder walls
to prevent rusting.