Rod,

With respect, you should have a fundamental objection to levying duty on marine fuel, at lesat at "road fuel" duty rates. There is no logical or ethical justification for levying a tax which, at least nominally, is intended to finance an infrastructure from which the taxpayer is benefitting when, in the case of boats, that infrastructure does not exist.

The absence of a tax IS NOT a subsidy - a point which many posters on these forumes consistently fail to grasp.