Installing Outboard To Boat Transom; Determining Recommended Outboard Mounting Height - Mercury Optimax 115 Service Manual

OUTBOARD MOTOR INSTALLATION

Installing Outboard to Boat Transom

Determining Recommended Outboard Mounting Height

Outboard
Mounting
Height (See
NOTE Below)
e
NOTE: Add 5 in. (127mm) for XL mod-
els and 10 in. (254mm) for XXL models
to listed outboard mounting height.
NOTICE TO INSTALLER:
1. The outboard should be mounted high enough on the transom so that the exhaust
relief hole will stay at least 1 in. (25.4 mm) above the water line when the engine is
running at idle speed. This will prevent exhaust restriction.
2. The mounting height (e) of the outboard must not exceed 25 in. (635 mm) for L mod-
els, 30 in. (762 mm) for XL models and 35 in. (889 mm) for XXL models. Mounting the
outboard higher may cause damage to the gear case components.
a. This solid line is recommended to determine the outboard mounting height. In-
b. These broken lines represent the extremes of known successful outboard mount-
c. This line may be preferred to determine outboard mounting height dimension, if
d. This line may be preferred to determine outboard mounting height dimension for
e. Outboard mounting height (height of outboard transom brackets from bottom of
Page 1D-2
26 in.
(660mm)
25 in.
(635mm)
24 in.
(609mm)
e
23 in.
(584mm)
22 in.
(560mm)
21 in.
(533mm)
20 in.
(508mm)
19 in.
(482mm)
10
creasing the height of outboard generally will provide the following: 1) Less steer-
ing torque, 2) more top speed, 3) greater boat stability, but, 4) will cause more prop
"break loose" which may be particularly noticeable when planing off or with heavy
load.
ing height dimensions.
maximum speed is the only objective.
dual outboard installation.
boat transom). For heights over 22 in. (560mm), a propeller, that is designed for
surfacing operation is usually preferred.
c
a
20 30 40 50
Maximum Boat Speed Anticipated
90-855347R1 JANUARY 1999
b
b
d
60 70 80