Refrigerated sea water (RSW) systems chill fish through a mechanical process that pulls heat from the catch within the fish holds into an evaporator, then discharges that heat overboard through a condenser. Most RSW units require between 5hp and 15hp, and this energy is supplied to the unit either hydraulically, electrically or through an auxiliary diesel engine.


RSW systems are regarded by most fishermen as the ultimate fish quality upgrade because they provide consistent results, create independence from an ice supply and require little additional effort to operate.


Good return on investment—For most fishing operations, RSW will provide a good return on the initial investment long term.Consistent chilling results—If operated properly, an RSW system will generally have no problem getting your fish down to temp, opening after opening.Independence—RSW allows you the freedom of not having to worry about getting ice before each opening, granting your operation more flexibility.Little effort required—RSW systems are easy to operate and require very little effort to operate on behalf of the captain or crew.No ice purchases—Not only does an RSW system save you the hassle of having to track down ice, it also eliminates that pesky ice bill.


Expensive—The primary drawback to an RSW system is the cost of the unit and related systems. Working up to RSW by investing in smaller upgrades over the course of a few years can make this more manageable.Increases fuel bill—RSW units require between 8 hp and 20 hp to operate and this extra work burns up to a gallon an hour more fuel, depending on the drive configuration. With high fuel prices this adds up fast.

10 Steps to RSW Chilling

1. Evaluation & Decision to Install

The benefits of installing an RSW system are obvious, but there is one barrier that prevents many fishermen from going this route. It’s expensive. A 7.5 ton hydraulically driven unit will run $20,000 or more, and that doesn’t include installation costs. Add a new 4-cube hydraulic pump, related plumbing plus insulation, and the total could fall in the $30,000 to $70,000 range, depending on your boat. These numbers can be daunting, but for most fishermen an investment in RSW will provide a solid return over the long run.



2. Research, Planning, Consultation with Vendors

Every boat is different, making every RSW install a custom job. A vessel owner will need to establish what chilling unit will best suit their needs and what hydraulic, plumbing, and fish hold upgrades need to be made to support the RSW system.

Direct consultation with RSW unit manufacturers is a good place to start. Presently, two companies supply most of the RSW equipment installed in Bristol Bay boats:

Apart from speaking with vendors, there are RSW consultants and dealers available to assist in planning out the entire project. Marine Refrigeration Solutions offers consultation services as well as installation services, marine refrigeration classes, and pre-season RSW start up services. Pacific West Refrigeration has dealers in both Naknek and Dillingham.

  • Marine Refrigeration Solutions...................360-204-6878 or 907-360-6600 or email

  • Brrr Refrigeration: PacWest Dealer (Naknek)............................907-942-5756

  • First Class Refrigeration: PacWest Dealer (Dillingham).............907-843-1161

3. Purchase

An RSW investment can run anywhere from $30,000 - $70,000 dollars depending on the vessel modifications you need to make to accommodate the system. This is no small chunk of change and, for most, this is not an out of pocket expense.

One approach to installing RSW that is more manageable, is investing in the necessary upgrades over a period of a few years. First insulating and plumbing your holds; the next year upgrading your hydraulics; and the following year going for the unit itself. Taking smaller bites out of the project helps maintain your fishing income, and reduce the potential of losing early-season fishing time by over-committing to a large project.

Another alternative is to seek financing. The State of Alaska, NOAA, BBEDC and Processors are all invested in the success of the Bristol Bay fishery and quality is an integral part of that success. For this reason many institutions and organizations offer non-traditional financing options.

  • SeaGrant through their FishBiz program has accumulated a very comprehensive list of financing options for fishermen. Click here for FishBiz financing resource page

The FishBiz website also offers extremely useful business tools custom created for commercial fishermen to help them Start, Manage, and Grow their business. We encourage all of our members to check it out!

  • The BBRSDA has secured a bulk rate discount on the purchase of 7.5T hydraulic drive, water cooled, RSW units manufactured by Pacific West Refrigeration. These units will be available at cost for resale to BBRSDA members on a first come first serve basis. Resale price is $18,450 per unit. Click here for more information.

  • The BBEDC offers a financing opportunity to residents of member communities specifically for RSW installs. If you are a watershed resident, find out more here.

  • SWAMC is offering Upgrade Grants through the US Department of Agriculture. The USDA grant reimburses owners for 25% of the cost for upgrades including slush ice to RSW, hold insulation, and high performance gensets (not for propulsion). To get started, visit, email:, or call Jamie Hansen at 907-450-2461.

  • Talk with your processor. They are invested in you and benefit from the quality improvement of your catch. They may be able to offer financial assistance as you make your RSW upgrade.

  • The Bristol Bay Borough is offering a one-time raw fish tax exemption up to $1,500.00 for fishing vessels that have installed new RSW systems after December 31, 2016. To apply, go to for more information or download the necessary form here.

4. Schedule Project

Plan it out. Coordinate when and where the parts and services for your install will take place, understanding that RSW manufacturers need lead time to produce your unit if it is not in stock, hydraulic, plumbing and fish hold upgrades will need to take place prior to the installation of your RSW unit, and that the whole project takes time. Start planning for your RSW upgrade in the fall to ensure you are ready to fish the following summer.

5. Shipping/Delivery

For many RSW upgrades, Bay boats will have to make the trip south. Unless you feel like a scenic tour of the Gulf of Alaska, you'll need to arrange for the shipping of your vessel.

  • Alaska Marine Lines offers barge service to and from the Bay. The BBRSDA has negotiated a discount for our members who are shipping their boats south for RSW install or upgrades. Contact AML and ask about the BBRSDA Fishermen's Boat Repair Program to qualify for the discount. Must be R/T transport from either Naknek or Dillingham to Seattle.

    • Alaska Marine Lines (Naknek)……………………..…..….…(907) 246-6667

    • Alaska Marine Lines (Seattle)…………………….….……..…800-826-8346

  • Again, talk with your processor. Many processors are moving their tendering fleets pre and post season. They may be able to work with you to coordinate the transfer of your vessel.

6. Fish Hold Configuration & RSW Unit Install

Prior to installing your unit, ensure your current fish hold configuration is capable of holding and insulating the proper volume of fish for your vessel and chilling capacity. Adding a couple of hundred pounds of equipment to your boat will reduce the amount of fish your boat can safely carry. Fish hold capacity may be further reduced by insulating your fish holds, which is mandatory on aluminum boats and strongly recommended on fiber- glass vessels.

An RSW system is an expensive piece of equipment, and like your boat’s engine, it needs to be protected from the elements. Your boat’s design will likely dictate the best place to install it. Depending on space, chilling equipment can be installed in or near the engine room, in the lazarette under a flush deck, amidships over the shaft alley, or even on deck in a weatherproof locker.

7. Plumbing

For RSW to work properly, your plumbing has to be correct. Fish holds need to be sealed; the water being chilled can not leak into the bilge or engine room. Typically a perforated pipe, draws water from the bottom of the fish hold and is pumped to the evaporator. The chilled water is then returned to the fish hold, often through a system of spray rails near the top edge of each hold. Some boats use a single or multiple hoses to return the cold water back to the fish hold, but spray rails have the advantage of ensuring the chilled water is well-mixed.

The water flowing through the condenser absorbs the heat captured from the fish hold and expels it over- board. The condenser water is drawn from below the waterline through a seacock and should pass through a filter to keep debris from clogging the system. A flow volume tuned to the requirements of your RSW equipment is required for maximum chilling efficiency, and inadequate condenser water can cause your chiller to shut down.

8. Hydraulics

Most small boats use hydraulics to power their RSW equipment, driven either by the boat’s main engine or by a small auxiliary engine. They can be also be powered electrically, but space considerations make installing an auxiliary generator difficult on small vessels.

A chiller rated at “7.5 tons of refrigeration” (more about that later) typically needs 10 gallons of hydraulic fluid a minute at 3000 psi.   That’s often more capacity than many small boats have. Unless your boat has hydraulic capacity to spare, you may have to upgrade your hydraulics.

9. Testing/Maintaining

It's never wise to hit the fishing grounds with untested equipment. After your install, and before the season starts, test run your system. This will give you time to make any modifications or repairs.

Be sure to educate yourself on basic maintenance, start up, and winterization of your system. Your RSW manufacturer should be able to provide you with a basic maintenance guide and Marine Refrigeration Solutions offers basic and advanced RSW courses. Find out more about Marine Refrigeration Solutions RSW Operator courses here.