Just noticed ... those boats have their engine running 24/7 now in the winter time. Perhaps to ensure the the engines are always ready to kick ass if there should be an emergency, despite the cold? Perhaps to keep the boat warm and cozy? Whatever the purpose, I can't help to think that the problem could have been better solved by using land power electricity from our hydro dams.
Image taken at Lysaker, Oslo, Norway. Full quality at IPFS QmZ31HmL1nb7r3R4aPtMheCsX8WCnNgJ994JcqXCKuCbRi. CC BY-SA 4.0