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This is THE Worlds Largest Forum devoted to the Norfolk Broads, here you can discuss issues about the Norfolk Broads. Or just somewhere to chat with others interested in the Norfolk Broads area. In 2015 forum members spent 2,048 days afloat on the Broads
You don't say which type of Powles 38 you have, if it is the seagoing flybridge version it is possible it exists - JPL Marine might be able to help, however if it one of the Broads designs, either centre or foward cockpit, then I doubt it either exist or was even the same boat to boat, the innards of these boats seemed to evolve over time rather than be designed!