The quantity of water that a fireboat can deliver makes a big difference. Your average fire engine in town delivers between 1000 and 1500 gallons per minute maximum. They are tied to firemains which have deposits and buildup inside them limiting their volume. Oftentimes the mains themselves are not capable of flowing as much as the eingine will in older sections of town.
Seattles new boat just recently put in service will flow in excess of 10,000 GPM. Tacoma's older fireboats (1983 vintage) will flow 7500 GPM. The difference between a 5 inch column of water and a 1.5 inch column of water provides much more penetration to the seat of the fire which is where extinguishment takes place.
The large nozzles can literally open up walls to get to the seat of the fire. Where land based companies are struggling to get inside the building for handlines (250 gpm), or open a path for master streams (1000 gpm) to get to the seat of the fire, the boat can make it's own opening.
Price of course is always a City's concern. How many fires will the boat respond to compared to a land company. How often will it be used compared to a land based unit? How much does it's upkeep cost? Then the bean counters do the math and cut the boats budget. At least that's what happens in my neck of the woods. Tacoma's boat typically responded less than 100 times per year while one of the south end engines took over 4000 calls.
We are currently renovating one of Tacoma's boats for about 4 million to take the place of the 2 boats that were in service up until 1999. The boats were originally designed with a 20 year service life. With minimal maintenance and repair only when totally broken they lasted 25 years. For example the engine oil was changed annually whether it needed it or not. 8V92's run against the governor don't pollute their oil very much do they?
Support from the boating community is important to keeping a fireboat in service. Boating groups, yacht clubs, port authorities, etc. all need to keep involved in making sure that funding keeps going to the fireboats.
Ken
Disclosure: Fireboat officer until budget cuts closed Fireboat Defiance in 1999.