Ok...Sorry for the late reply...Been busy...Not making any money, but busy...
First..."Chiller" is a term that is generally used to describe a Chilled Water condensing unit...It's the part of a Chilled Water system that chills the water that is pumped out to the "Air Handlers" instead of freon....You do not have a Chilled Water system...You do have what is called a "Direct Expansion Split (or Remote) System"
In your case (as with most all older Hatteras's below about 77') the "Condensing Unit/s" are Remote (eng rm etc) and the "Air Handlers" are in the space to be cooled/heated...
"Self Contained" direct expansion units combine both the Condensing unit & the Air Handler on one base & it is installed in the space to be cooled/heated.
Now that we got that over with...
Yes your older style Air Handlers were "Blow Thru" type (as opposed to newer "Draw Thru) They were noisy & didn't move much air (1960's design)
I'm guessing, but it was very common for Hatteras to install a EFL-16 (twin blower) unit in the salon that is connected to a WFAH-16 Condensing unit remotely located.
The staterooms were likely EFB-X (X being the BTU size) So maybe two EFB-6's controlled by a three knob control in the master...The fwd EFB only had fan speed control, was not meant to shut off, it ran with the master unit....Both of these Air Handlers would have been connected to a Remote WFAH-12....Total air handler BTU must match the compressor/condensing unit BTU...The 3 knob control in the Master, controlled Master AH fan speed, sensed temp in the master, and cycled the compressor on Master stateroom temp.
There is not much you can do with those EFB/EFL air handlers to quiet them down except adjust the fan speed control (little screw inside thru a hole in the side under a sticker) to a lower setting when the knob is fully CCW....Thing is...The EFB/EFL's didn't really move enough air in the first place, and slowing them down only causes the air coil to ice in cooling, or the unit to cycle on high head pressure in heat....Either being really hard on the compressor...Add to this 30 or so years of dust further restricting the air coil, and the problem compounds itself...
You can retrofit to newer style air handlers that have squirrel cages that move more air, and are quieter, but you are still dealing with 30 year old condensing units that are R-22 refrigerant that is getting more & more expensive, and those old units are less efficient (like 27%)
This post in my forum might explain more about refrigerants:
http://marine-ac.com/2010/01/27/marine-ac-new-refrigerant-regulations/
You can also go the Self Contained unit route as you mentioned however I have not heard good things about the Webasto units (from the other service guys I meet in schools)....Mermaid is Ok for a bargain unit....
I sell Dometic (new owner of Cruisair & Marine Airrr) and just picked up MarinAire as a lower cost alternative, but the Dometic "Turbo" units are hard to beat in all ways except price...
http://www.dometic.com/enus/Americas/USA/Marine/Marine-Air/DX-Self-Contained/
Retail Pricing for Cruisair & Marine Airrr is on my site (price increase due the first of the year) but they won't let me quote discounts publicly.
I don't yet have MarinAire pricing listed on site...Just got the dealership yesterday but I can sell for the same pricing listed on their site:
http://www.marinaire.com/Products_s/12.htm
If you want to talk about just the air handler upgrade/s we can do that too...
Steve~