Shaft-Transmission Alignment; Checking Alignment; Shaft Log Stuffing Box Packing - Bayliner 3788 Command Bridge Owner's Manual

14 CHAPTER 3: COMPONENTS / SYSTEMS

Shaft-Transmission Alignment

• Alignment between the engine transmission output shaft and the propeller shaft is critical. This alignment has
been performed at the factory, and was rechecked by the dealer after the boat had been in the water for 48 hours.
• An alignment inspection should be performed as part of the routine maintenance program (after the initial 30
hours of operation, then every 60 hours) and whenever unusual noise or vibration is noticed.
• To insure proper alignment after a hallout or dry storage, wait 48 hours after launching before making final
alignment adjustments.

Checking Alignment

Engine alignment requires moving the engine and should be per-
formed by a marine mechanic. However, checking the alignment is rel-
atively simple when these steps are followed:
1. Remove the flange bolts at the transmission-to-prop shaft coupling
and slide the shaft aft until the flanges are about 1/4" apart.
2. Rotate the shaft to see if there is obvious "wobble" of the shaft
flange. If there is, it may indicate shaft damage and should be
inspected by a marine mechanic as soon as possible.
3. Move the shaft up and down and from side to side to determine, as
closely as possible, the central position where the shaft is normally
located. At this position, the transmission flange should align with
the shaft flange without moving the shaft more than 1/8". If this is
not the case, a misalignment condition exists.
4. Move the shaft flange into contact with the transmission flange.
5. Check the gap between flange faces by attempting to insert a 0.003" feeler gauge at the top, bottom and each side.
6. Repeat this operation after rotat-
ing the shaft flange 1/4 turn (3
times). If the feeler gauge can be
easily inserted at any point, a
misalignment condition exists
(see CAUTION on right).
7. Reinstall the flange bolts, nuts and lock washers (if provided) and
torque to the specifications listed to the right. Replacement bolts, nuts
and washers must be corrosion resistant and grade 8 or better.

Shaft Log Stuffing Box Packing

The propeller shaft emerges from the bottom of the yacht through an opening called the shaft log. The shaft stuffing
box is connected to the shaft log by a short length of special flexible hose. Packing rings are compressed around the
shaft by the packing gland. The stuffing for the box prevents excessive amounts of water from leaking around the
shaft and into the boat. Normal wear can cause stuffing box leakage to increase. Excessive leakage can usually be
stopped by tightening the packing gland nuts slightly. DO NOT over tighten the packing gland nuts. A slight leak (up
to 10 drops per minute while running) is normal and helps lubricate the packing and is therefore NECESSARY.
When stuffing box leakage becomes excessive, even after following the above steps, packing replacement can be per-
formed as follows;
1. Remove the yacht from water.
2. Loosen the packing gland nuts and back the packing gland from the sleeve. Remove the old packing.
3. Wrap new packing around the shaft (4 rings, 3/16" for 1 1/2" shafts), then cut the rings with a razor blade at an
angle approximately 30 degrees to the long axis of the shaft. Stagger the ends of each ring around the shaft and
insure that the ring are at the bottom in the sleeve.
4. Tighten the packing gland nuts until resistance is felt.
When initially launched, the packing must be allowed to leak at a rate of 5 to 30 drops per minute, as it will expand
and seal from water contact and friction heat from the turning shaft. Failure to allow this leak-off will result in pack-
ing burnout after a short period of time.
3788 Motoryacht • Owner's Manual Supplement
If a shaft misalignment exists, have a qualified marine mechanic per-
form an alignment as soon as possible. Continued use may lead to pre-
mature engine, transmission, shaft, shaft seal and/or hull damage.
TYPICAL TRANSMISSION-TO-PROP SHAFT COMPONENTS
NOTE: TRANSMISSION-TO-PROP SHAFT COMPONENTS
VARY DEPENDING ON ENGINE TYPE AND SIZE.
CAUTION
!
BOLT SIZE
3/8" - 24 - - - - - - 40 lbs. (+/- 7 lbs.)
7/16" - 20 - - - - - 65 lbs. (+/- 10 lbs.)
1/2" - 20 - - - - - - 95 lbs. (+/- 15 lbs.)
5/8" - 18 - - - - - - 200 lbs. (+/- 30 lbs.)
M16 x 1.5 - - - - - 175 lbs. (+/- 25 lbs.)
TORQUE