When full of water the heater has a substantial mass. It must be secured firmly in place to prevent damage to the heater and pipework or to the supporting structure, from the effects of rough weather or other shocks of marine use.
1. Support the WEIGHT on a strong base.
2. Support the MASS against horizontal forces.
The exact method you use to hold the heater in place will depend on the construction of the vessel and on the available space.
Some suggested installation methods are indicated below.