Silverton 33C - Trim Tab System

SYSTEM OPERATIONS-65
The purpose of the Trim Tab System on your 33C
is to assist in reaching planing speed as soon as
possible and to maintain a proper “running attitude”
while in forward motion. “Running Attitude” is de-
fi ned as the level of the boat, both fore and aft and
athwartships, while the vessel is underway. Your
yacht, upon reaching planing speed, should rise
slightly in the bow and should not list to either side for
the greatest stability and fuel economy. Your 33C is
equipped with two (2) Bennett Trim Tabs, each mea-
suring 12” x 24”, which are mounted on the trailing
edge of the transom (See photograph below, which
illustrates the location of the Port trim tab).
Each Trim Tab operates independently of each other
and they are controlled by separate rocker-type
switches, located on the Helm Switch Panel (Refer
to the Electrical Pages in this section of this Owner’s
Manual for the location of these switches). Each
Trim Tab is actuated by a hydraulic cylinder, which
moves them in an Up or Down motion.
The position as determined by depressing the rocker-
type switches as follows:
Depressing the TOP of the switch lowers the
Trim Tab.
Depressing the BOTTOM of the switch raises
the Trim Tab.
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•
The Trim Tab System operates in the following
manner:
 The function of the Trim Tab is to redirect the fl ow
of water beyond the bottom of the Transom. This
creates an upward pressure on the hull bottom at the
Transom, which results in lowering the bow.
 When the Port Trim Tab is lowered, the Port stern
section is raised, which lowers the Starboard side
of the bow.
 When the Starboard Trim Tab is lowered, the
Starboard stern section is raised, which lowers the
Port side of the bow.
 Both Trim Tabs should be lowered/raised as
needed to maintain a proper “Running Attitude”.
Operation of the Trim Tab System may require
practice to attain a level of profi
ciency. DO NOT
operate either Trim Tab to its extreme lowered
position suddenly. This may cause the bow to
lower to an unsafe position while heading into
or away from waves, which may cause “swamp-
ing” of your yacht, resulting in possible injury
or death. DO operate the Trim Tab switches
with short “bursts” until the desired “Running
Attitude” is obtained.
Maintenance of the Trim Tab System is as fol-
lows:
 Silverton recommends painting the Trim Tabs with
good quality, antifouling bottom paint. DO NOT paint
any hinges or the moving parts of the cylinders.
 To reduce the risk of electrolysis and galvanic
corrosion, Silverton recommends the installation of
Sacrifi cial Zinc Anodes on the Trim Tab plates at least
once a year, preferably during preparation for spring
launch. DO NOT paint the Sacrifi cial Zinc Anodes.
TRIM TAB SYSTEM