I should know the answer to this but what was the final outcome for red in the UK? Was it completely abolished in the end? What the prices at marine pumps now?
Each time you fill up, you declare the amount to be used for propulsion on a bit of paper. The propulsion part gets taxed at full whack, and the amount to be used for "heating" or other uses gets taxed at the lower rate. If you declare 60% propulsion, 40% "other", HMRC have said you are unlikely to get investigated as to the actual usage.
Pump prices are often displayed as this "60/40" price, which is around 90-something per litre in the Solent.
Ouch - exactly. Which is why reasonably economical (for a boat) 35-38ft boats on outdrives are selling a bit better than thirsty flybridges on shafts at the moment.