They are high maintenance and have a high fuel consumption.
They hull's are very susceptible to irreparable damage from heavy weather due to the aluminium construction.There a few tied up around the world with irreparable hull damage from bad weather.
Re;the B.C. Ferries modified the design to lighten them to limit fuel consumption ergo the car deck's can not take semi's etc. and have smaller fuel tanks.First trip into Nanaimo they took on 30,000 Lt.'s of fuel.
The Engines are V 24 MTU high speed diesel's with Kamewa water jets.
The engines have to have a oil change every 700 hrs at something like $25.00 a Ltr. a special oil for high speed diesel engines,I forget the capacity.
Valve lash had to be checked every 200 hrs or so if I remember rightly and I could go on about the servicing of the beasties. :
What was fun was watching the passengers up chucking in a bad sea state ;D Fast Pussies and their cousins don't roll and pitch like a mono hulled ship.Also the B.C. Ferry Pussies have a limited sea state they are allowed to sail in due to the hull design which they made to fit the present ferry dock's in H.Bay and Nan. and if I remember right it about a 1.8 m sea state which is not much if you have seen what the Straite of Georgia can throw at you when a good south easter realy blows.
The only thing they did right was the high pressure refueling system,30,000 Ltr.'s in 20 min.