In the Netherlands grease lubrication is commonly used for many years. It’s a relative cheap systeem. To be sure of sufficient lubrication, grease has to be supplied to the stern tube under minor pressure. In most cases a manually operated spindle lubricator is being used but it’s also possible to install an automatic electrical or mechanical driven lubricator.
Lubrication is not allowed to be neglected; irreparable damage can be the result. When the stern tube is well filled with grease, in practice hardly any water will come into the boat, even when the vessel is moored.
Optionally the stern tube can be executed with a sealing at the rear side (propeller side), possibly combined with a connection for a ‘grease-return’.