The self propelled boat trailer for marinas Sublift 12t handles boats with a maximum weight of 12 ton and a width up to 4,4 m. The frame on the Sublift is of an open U-type enabling easy loading and unloading of a boat to and from its supports. The Sublift makes it easy to bring a boat on land to wash the bottom and do other work where the boat needs to be out of the water. This enables boat owners to use less toxic paint and therefore save both the environ-ment and money. It is easier to lunch the boat out of the water twice a year and wash it than to paint the hull with toxic paint.