I have had a battery failure so need to change most of the batteries. All 5 of which 3 are large (50 cm x25 cm) are squeezed into the base of one side of the saloon seating. There is no space between the batteries and the timber base. I had thought I could remove the timber top but this one piece and glassed in. These can,t be original -boat is 15 years old so there must be a way to remove. My replacement batteries are same size.
Any help much appreciated