Yanmar ZT350 series, Installation Manual

Page: 26 / 80

INSTALLING ENGINE AND DRIVE UNIT
4-4 ZT350 Installation Manual
Positioning the Drive Unit
© 2007 Yanmar Marine International
Finding the Crankshaft Horizontal
Centerline (X-Dimension)
There are two general methods available for
locating the horizontal centerline of the engine
crankshaft. They are the “90° Tool Method” and the
“Tape Measure Method”. Regardless of the method
used, several vessel design considerations need to
be examined before an optimum determination can
be made. The following suggestions are offered as
a general guideline. The actual “X-Dimension”
should be the result of thorough design testing by
the hull manufacturer.
NOTICE: When the X-dimension is increased, the
pulling power for skiing is decreased. During
testing, increase the X-dimension in 13 mm (1/2 in.)
increments until preferred performance is achieved.
Never increase the X-dimension by more than:
Observe the following details during the testing
process:
• Ensure that the water supply does not become
aerated when the drive unit is raised.
• Use a clear water inlet hose to monitor incoming
water while watching the engine temperature
gauge to prevent the engine from overheating.
NOTICE: Damage to Yanmar products caused by a
crankshaft horizontal centerline that is too high, will
not be covered by Yanmar warranty.
The 90° Tool Method
Construct the 90° tool as shown in Figure 4-3 .
Figure 4-3
Figure 4-3
1 – 345 mm (13-9/16 in.)
2 – 1.2 m (4 ft)
NOTICE: The 345 mm (13-9/16 in.) dimension
should only be raised or lowered after proper
testing (See Finding the Crankshaft Horizontal
Centerline (X-Dimension) on page 4-4).
• To lower the drive unit - subtract from the 345 mm
(13 9/16 in.) dimension (Figure 4-3, (1)) .
• To raise the drive unit - add to 345 mm
(13 9/16 in.) dimension (Figure 4-3, (1)) .
Use the 90° tool as follows:
1. Place the 90° tool along the boat bottom at the
vertical centerline.
2. Locate the point at which the top of the 90° tool
contacts the transom on the vertical centerline.
3. This is the crankshaft horizontal centerline or
X-dimension.
Vessel Characteristics
Speeds Below 22 Knots
(25 mph) Subtract 13 mm (0.5 in.)
from X-Dimension
Heavy Duty Applications
Subtract 25 mm (1.0 in.)
from X-Dimension
Speeds Between 22 Knots
(25 mph) and 43 Knots
(50 mph) Use the X-Dimension
given in the 90° Tool
Method
Speeds Above 43 Knots
(50 mph) Increase the X-Dimension
to improve performance.
Maximum Increase in X-Dimension
ZT350 25 mm (1 in.)
90˚
(1)
(2)