Owner`s manual

MARINE TRANSMISSIONS
Marine transmissions fall generally into two groups, mechanical shift or hydraulic shift.
Mechanical transmissions connect the input from the engine to the output of the shaft by
means of a mechanically operated assembly such as a dog clutch or shift fork that
mechanically moves the gears into the selected position. Hydraulic transmissions
connect the input from the engine to the output at the shaft by means of a hydraulically
operated piston, which clamps the clutches or friction plates together locking the input
shaft to the output gear.
Since we are focused on the Westerbeke product in the Gemini, we will stick with the
mechanically operated transmissions. Westerbeke model 30B-Three engines have been
assembled with three model transmissions. The earlier models used a Hurth model
HBW100. The current engines use a Westerbeke JS gear or a Newage PRM gear. While
all are mechanical transmissions they differ in their operations.
The Hurth Gear uses a servo-automatically controlled helical gear. The servo-operated
multiple disc clutch system requires only minimum effort to shift. The Hurth gear is
immersion lubricated. And maintenance is restricted to oil level checks, fluid changes
and visual inspections.
The JS transmission is similar to the Hurth. It, however, uses a cone clutch to engage the
gears. The JS gear also uses the immersion lubrication method. This transmission cannot
be shifted from full ahead to full astern. All shifting must be done below 1200 rpm’s.
When shifting any modern mechanical transmission used by Westerbeke, the lever must
be moved in a snappy motion, slowly moving the lever may not engage the clutches.
Fluid checks are simple. Remove the dipstick, wipe it clean, reinsert into transmission,
remove and check. The fluid level should be at the top mark on the dipstick.
Any indication of a malfunction can be either seen or smelled from the oil on the
dipstick.