SECTION P Gearbox, Flywheel & Flywheel Housing GEARBOX The gearbox fitted to the 4.236 Marine engine is the earlier   Borg   Warner   71   CR   or   the   later   10-17   type, hydraulically  operated,  direct  drive  type  incorporating  a reverse gear. A   Borg   Warner   71   CR   or   the   later   10-17   type gearbox with an epicyclic reduction gear can be supplied with  the  following  ratios:–  1.523:1,  1.91:1,  2.1:1,  2.57:1, or  2.91:1.    The  output  shaft  of  the  gearbox  or  reduction gear is on the same centreline as the crankshaft. For  standard  gearboxes  and  reduction  gear,  a  left handed   propeller   is   required,   except   with   the   1.91:I reduction  gear,  which  requires  a  right  handed  propeller. The   2.1:1   and   1.91:1   reduction   gears   can   be   used together in twin engined installations to give left and right handed propeller rotation. The    gearbox    operating    oil    pressure    should    be 120/140 lbf/in² (8,4/9,8 kgf/cm²) - 827/965 kN/m². IMPORTANT NOTE: When filling the Borg Warner gearbox as fitted to the 4.236  Marine  engine,  Automatic  Transmission  Fluid Type 'A' must be used. The  gearbox  should  be  filled  to  the  full  mark  on  the dipstick  and  the  unit  turned  over  at  low  speed  by  idling the  engine  for  a  short  period  in  order  to  fill  all  circuits including the cooler and cooler piping. The  oil  level  should  then  be  checked  immediately after  shutting  off  the  engine  and  sufficient  oil  added  to bring the level to the full mark again. When   checking   the   gearbox   oil   level,   the   dipstick should   be   screwed   fully   home   in   order   to   obtain   the correct reading. TO REMOVE THE GEARBOX 1. Remove    lubricating    oil    pipes    to    and    from gearbox oil cooler. 2. Remove water connections to and from gearbox oil cooler. 3. Remove gearbox oil cooler. 4. Uncouple   propeller   shaft   from   gearbox   output shaft and move clear of box. 5. Remove nuts securing gearbox adaptor plate. 6. The gearbox can then be removed by withdrawing it to the rear. 7. Remove  nuts  securing  gearbox  adaptor  plate  to flywheel housing. 8. Remove adaptor plate. 9. The driving plate connecting  the  gearbox  to  the flywheel   can   now   be   removed.      It   should   he noted  that  if  either  flywheel  or  flywheel  housing .is  removed,  then  it  must  be  accurately  aligned on replacement in accordance with the instructions on Pages P.2 and P.3. TO REFIT THE GEARBOX Replacement of the gearbox is the reverse procedure  to  removal  but  the  splines  on  the  gearbox input  shaft  should  be  lubricated  with  anti-fretting  grease before the unit is replaced. Fig. P.1.  Gearbox to Flywheel driving plate.