Yamaha 33 1980 Owner's Manual page 17

Y33 2-4
2-2-3. The Adjustment of the Upper Shrouds:
Adjust the upper shrouds until the masthead is equal distant from each chainpiate(see Fig. 13).
Use the main halyard or a steel tape measure to check the athwartship alignment.
Set up the shrouds to have 50 mm/2 in of play (see Fig. 12).
HALYARD
UPPER SHROUD
Fig. 13
2-2-4. The Adjustment of the MIdstay:
Set up the midstay (inner forestay) until it pulls the mast forward 25 mm/1 in at the spreader
brackets.
This figure may vary but should be between 20 mm to 40 mm according to the cut of the main sail.
The play of the midstay is 55 mm/2 in 1/8.
2-2-5. The Adjustment of the Lower Shrouds:
Set up the lower shrouds tight until they start to pull the mast aft.
The play of the lower shrouds will be 30 mm/1 in 1/8.
NOTE: 1) SIGHT UP THE MAST WHILE THE BOAT IS UNDER WAY.
IT SHOULD BE STRAIGHT IN ITS GROOVE AND LEEWARD SHROUDS SLACK
WHEN ON THE WIND.
2) REMEMBER, DO NOT TIGHTEN THE STANDING RIGGING MORE THAN NECES
SARY. OTHERWISE, HULL DAMAGE MAY RESULT.
3) DO NOT ATTEMPT, OR AT LEAST BE VERY CAUTIOUS TO CORRECT MAST
CURVATURE UNDER WAY. RIGGING ON THE LEEWARD SIDE IS NORMALLY
QUITE SLACK WHEN A BOAT IS HEELED, AND IT IS EASY TO ADJUST IT TOO
TIGHT WHICH CAN DESTROY THE PROPER TUNE AND PUT A GREAT STRAIN
ON THE BOAT.
4) THE HEAD OF THE MAST SHOULD NOT "HOOK" TO WINDWARD.
IF NOT STRAIGHT, IT WOULD BE MORE DESIRABLE TO HAVE THE HEAD