Transom Height Of The Boat; Locate Centerline Of The Outboard; Outboard Mounting Height - Mercury 15XD Service Manual

Transom Height of the Boat

Outboards with jet drives will be mounted approximately 7 inches higher on the transom
than propeller driven outboards. This requires outboards that have a 15 in. shaft length
to be installed on boats having a 22 in. transom height and outboards that have a 20 in.
shaft length to be installed on boats having a 27 in. transom height.
If the boat transom is of insufficient height, and the outboard cannot be installed to the
recommended height, contact the boat manufacturer for recommended procedure to
build up the boat transom.

Locate Centerline Of The Outboard

Locate (and mark with pencil) the vertical centerline (a) of boat transom.
a -

Outboard Mounting Height

The initial outboard mounting height setting will work good for most applications, however,
because of different boat/hulls designs, the setting should be rechecked by test-running
the boat. Refer to Water Testing.
· Installing the outboard too high on the transom will allow the water intake to suck
in air and cause cavitation. (Cavitation will cause the engine to overspeed in spurts
and reduce thrust). This condition should be avoided by proper height setting.
· Installing the outboard too low on the transom will allow excessive drag.
SETTING OUTBOARD MOUNTING HEIGHT ON BOATS WITH "V" BOTTOM HULLS
1. Measure the width of the leading edge on the water intake housing. Make a horizontal
line (a) on the transom up from the " V"bottom the same length as the width of the water
intake housing (b)
a -
b -
90-826883R2 JUNE 1998
A
C
Centerline of Transom
Horizontal Line
Width of Water Intake Housing
B
a
D
a
b
JET DRIVE
Page 6B-11