Abnormalsheep it looks like someone has added extra superstructure to the front of your boat. the front well drain outlets on a Swanline boat would normally be at the back of the front well deck. The photos at the very start of this thread do not look like any of the Swanline boats that I remember. If its an original hireboat then it would have had a black hull, green roof, white sides with a red line (approx 4inches deep) above the gunwale
The Swanline hire boats were fitted with one of four engines between 1970 and 1980 that I know of. They are the Lister SR2 for the 36ft & 45ft Steel hull/GRP superstructure, Lister SR3 for the 58ft all-steel, Lister ST2 for the early 32ft 6in and 49ft all-steel boats and the Petter 1500 watercooled marinised VW Golf engine for all the 39ft all-steel boats.