Oyster and Remora Screws should be tightened up to a torque of 0.7 Newton metres (Nm). 

Tighten the screws gradually, partially tightening each screw in turn - rather than tightening one as hard as it can go before moving on to the next screw.

Also make sure that the seal is clean, seated properly and in good working order.

How much is 0.7Nm?

This can be checked with a torque screw driver. Many installers do not have access to torque screw drivers, and will be installing with various portable drilling machines or manual screw drivers. Care should be taken not to over tighten the screws. 

Over tightening to a torque of 1.2Nm will start to fracture the screw bosses. This must be avoided at all costs as the IP rating will be compromised.

To test the required tightness without a torque wrench, screw a housing together and note any notches formed on the base, on the rim next to the screw holes. If notches start to form, the torque is too high. These notches are the cover bottoming out on the base. They should be avoided.

Notches like this in the base should be avoided:

The result of extreme over tightening: