Technical data

BW TRANSMISSIONS
(BW3, BW&, BW12)
These manual transmissions rotate opposite to the engine when in forward gear. Shifting effort is very
low. The input power on the BW3 is transmitted to the output shaft by helical spur gears when in
forward. In reverse this task is taken over by a high performance roller chain. The unit also incorporates a
servo cone-type clutch. The BW7 and BW12 transmit their power with casehardened helical gears and in
reverse there is an intermediate gear. The reversing process on these is carried out by a servo double disc
system.
LUBRICATION
1. Fill the transmission with 20 to 40 SAE weight engine oil, the same as is used in the engine.
2. Oil capacity
BW3 approximately 0.35 liter BW7 approximately 1.0 liter
BW12 approximately 1.0 liter
3. Check the oil level daily with the engine stopped. The level must be between the upper and lower
dipstick marks when the dipstick is completely screwed/inserted into the housing.
4. Change the oil initially after the first 30 hours, thereafter every 250 hours, once per year minimum.
The BW7 and BW12 have a drain plug for oil removal. Oil may also be removed by suction through
the dipstick tube, where oil is added.
5. Operating oil temperature must not exceed 120'C (250'F).
OPERATION
1. Normal shifting should be done below 1500 RPM.
2. The BW3 may be locked in reverse when sailing or freewheeled in neutral.
3. The BW7 and BW12 may be locked in either forward or reverse when sailing or freewheeled in
neutral.
SERVICE
1. Never loosen the shift lever cover screws, except in the course of qualified servicing, as this upsets a
critical adjustment.
2. Disassembly of the transmission in the field is not recommended. If an overhaul or repair is needed,
the work should be done by Westerbeke or an authorized Westerbeke service center.