Kongsberg Simrad SN90 Reference Manual page 295

Note
If you suspect that the gasket is damaged, replace it. If the gasket has been
contaminated with dirt, grease or lubricants, it must be replaced.
9 Lower the hull unit carefully onto the installation trunk.
Important
The transducer is covered with a thick red or black protective coating made of a
special plastic type. The protective coating is a vital part of the transducer. It is
very important that neither this coating nor the internal parts of the transducer are
damaged during the handling, installation or cleaning.
10 Align the mounting holes carefully.
11 Mount and tighten the relevant nuts and bolts.
First, tighten all the nuts to finger tight. Then work alternately on opposite sides of
the construction.
Use the following torque: 140 Nm
381294/E
Maintenance procedures
293