...
Southern Boating & Yachting
  • Boats
    • Center Consoles
    • Dual Consoles
    • Motoryachts
    • Power Cats
    • Sport Cruisers
    • Tenders & Ribs
  • Destinations
    • Regional Reports
    • Bahamas
    • Caribbean
    • U.S. Atlantic
    • U.S. Gulf
  • Engines
  • Maintenance
    • DIY
  • Electronics
  • Lifestyle
    • News
      • Boating Log
    • Fishing
    • Food
      • Menus
      • Drinks
      • Appetizers
      • Entrées
      • Dessert
      • Holiday
  • Gear
  • Shop
  • Digital Edition
  • Subscribe
  • Advertise
No Result
View All Result
  • Boats
    • Center Consoles
    • Dual Consoles
    • Motoryachts
    • Power Cats
    • Sport Cruisers
    • Tenders & Ribs
  • Destinations
    • Regional Reports
    • Bahamas
    • Caribbean
    • U.S. Atlantic
    • U.S. Gulf
  • Engines
  • Maintenance
    • DIY
  • Electronics
  • Lifestyle
    • News
      • Boating Log
    • Fishing
    • Food
      • Menus
      • Drinks
      • Appetizers
      • Entrées
      • Dessert
      • Holiday
  • Gear
  • Shop
  • Digital Edition
  • Subscribe
  • Advertise
No Result
View All Result
Southern Boating & Yachting
No Result
View All Result
Home Maintenance DIY
A man holds a clean Marine AC pipe

DIY Marine AC Maintenance Advice: How to Stay Cool on Board

Stay Cool

May 6, 2025
in DIY, Maintenance
0
644
SHARES
3.6k
VIEWS
Share on FacebookShare on LinkedInShare via Email

Simple DIY Chores to Maintain Your Marine AC

Air conditioning aboard your boat is a wonderful luxury, dockside or underway. Fortunately, it’s an easy DIY to keep your marine AC running and stay cool.

How it Works

To troubleshoot your marine air conditioner, you should understand how the system works. A home air conditioning system has an air handler or blower fan inside your house, and the outside compressor unit contains condensing cooling coils. 

The big difference between the marine and the home unit is the method of cooling the refrigerant. The home air conditioning unit uses a very large cooling fan outdoors. Your marine air conditioner uses a raw-water pump to circulate water through the condensing cooling coils inside the boat hull belowdecks.

In your bilge, there is a seacock which is an on-off valve. The seacock connects to the sea strainer via a double-wall hose with double stainless steel hose clamps. The sea strainer captures any debris and prevents it from entering and damaging the water pump.

Also Read

running shot of Marlow Avalon 65

Inside the Bold New Marlow Avalon 65 Yacht

August 18, 2025
3.5k

Built by the company’s namesake, the Marlow Avalon 65 is the yacht David Marlow always wanted. Walking down the dock...

Air conditioning aboard your boat is a wonderful luxury, dockside or underway. Fortunately, it’s an easy DIY to keep your marine AC running and stay cool.

How it Works

To troubleshoot your marine air conditioner, you should understand how the system works. A home air conditioning system has an air handler or blower fan inside your house, and the outside compressor unit contains condensing cooling coils. 

The big difference between the marine and the home unit is the method of cooling the refrigerant. The home air conditioning unit uses a very large cooling fan outdoors. Your marine air conditioner uses a raw-water pump to circulate water through the condensing cooling coils inside the boat hull belowdecks.

 

In your bilge, there is a seacock which is an on-off valve. The seacock connects to the sea strainer via a double-wall hose with double stainless steel hose clamps. The sea strainer captures any debris and prevents it from entering and damaging the water pump.

Another double-wall hose with double stainless steel clamps connects the sea strainer to the raw-water cooling pump. The hose then flows raw water to the air conditioner condensing coils and compressor unit. This raw water will cool the refrigerant. That water is then discharged overboard near the location of the condensing coils. The cool refrigerant flows to the air handler, and the fan blows cool air into the stateroom. Got it all? Now you are cool.

Subscribe Here For More Boating Content

Can’t Stay Cool?

When things aren’t cooling down, then what do you check? First, look at the wall control panel. If it shows HI P5 or HIP, that indicates high pressure—the 5 represents an S. High pressure is caused by hot refrigerant not being cooled with sufficient raw-water cooling flow.

Next, check the overboard water discharge to confirm it is flowing. Two air conditioning units should have two overboard discharge streams. If no stream is noted, verify that the water pump circuit breaker is ON. Then check the seacock valve handle to ensure it is open. Now inspect the strainer to make sure it is not fouled with debris, such as barnacles and algae. If all checks are okay, then confirm the pump is running. 

Air Lock in the Marine AC

If the system is not clogged but the pump is running, you may have an air lock in the pump system. The more common pumps I see aboard boats are not self-priming, so you may have to prime the water pump. 

How did the pump get air in it? If the boat is hauled out at the boatyard, the water may drain out of the air conditioning system. Close the seacock before hauling out for service, especially if your boat is dry-stored. Another cause of losing prime could be as simple as running the air conditioner while crashing through rough white water. The white water you see is actually air and the air conditioning system may be ingesting that air causing it to lose prime. 

Keep OUT the Critters to Keep Cool

The condensing cooling coils have a tube inside of a tube and act as a heat exchanger similar to the heat exchangers on your engines. Marine life can grow inside the coils restricting heat transfer. And just like your main engines, you must do periodic cleaning of these coils. A simple preventive DIY maintenance is to use a product such as Barnacle Buster and recycle it through the coils until you see clear fluid.

Marine AC Refrigerant

To flush your air conditioner coils, grab a five-gallon bucket and a small bilge pump to attach to your battery. CAUTION: For gasoline boats, because of arcing and sparking concerns, be sure you have a hard-wired battery connection to the small bilge pump. Run a temporary hose into and out of the cooling coils back to the bucket to flush the system. Simple, messy, yet efficient to clean your coils.

Keep Clean Filters and a Clear Drain Hose

Just like your home air conditioner, the air filters should be changed often. Many boat air handlers pull in return air near the floor where all the dirt and dust collect. If your air handler coils are clogged with dust, it will become wet with condensation and grow mold and mildew. Keep ahead of this simple task, more often if you have pets aboard.

A dirty Marine AC filter

And last, you may notice condensation on the floor. This can be caused by wet dust plugging the condensate drain hose. Be sure to locate and clear that drain hole and hose. A long pipe cleaner should be in every boater’s onboard toolbox for this task. Many boats now drain the air conditioner condensate into the under-floor shower sump box.

A man holds a clean Marine AC pipe

To DIY or Not

A wall control panel displaying LO P5 means low pressure. This is low refrigerant and means you have a refrigerant leak. You may even notice an ice ball near the compressor. No DIY here. Call a technician.

Otherwise, these simple DIY chores can save your weekend cruise and help you stay cool. 

-by Chris Caldwell

Related Posts

Man cleaning hull of boat with a buffer
DIY

Experts Share 5 Fall Maintenance Tips Every Boat Owner Should Know

August 20, 2025
3.3k
view of boat's aft on a boat lift that is in the water
DIY

A Summer Survival Guide for DIY Boat Lift Care

August 19, 2025
3.4k
Jack plate control used during shallow-water fishing
DIY

Is This The Best Anchoring Gear for Shallow-Water Fishing?

June 24, 2025
3.4k
A golden propeller showing the end of this boat's steering system after a DIY project
DIY

Boat Steering Systems 101: A DIY Inspection and Repair Guide

May 28, 2025
3.6k
Ceramic Coat for boats
Haul-Out Guide

Ceramic Coating vs Wax for Boats: What’s the Best Protection?

April 8, 2025
4k
Lumitec Expands Warranty to 5 Years on Marine LED Lighting
Electronics

Lumitec Expands Warranty to 5 Years on Marine LED Lighting

March 18, 2025
3.4k
Subscribe to the print magazine | $29.95 for 12 issues
Previous Post

This Hatteras 41C Refit Was Worth Every Dollar: Budget Breakdown + Real Advice

Next Post

Yanmar Marine on the Advance Powers Innovation in Recreational Tech

Next Post
Two Yanmar Marine products with a green to white gradient background

Yanmar Marine on the Advance Powers Innovation in Recreational Tech

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Recommended

upgrade your electronic

Upgrade Your Electronics

October 13, 2018
3.3k
Top Tenders and RIBS of 2021

Top Tenders and RIBS of 2021

August 2, 2021
10.7k

Don't miss it

Man cleaning hull of boat with a buffer
DIY

Experts Share 5 Fall Maintenance Tips Every Boat Owner Should Know

August 20, 2025
3.3k
view of boat's aft on a boat lift that is in the water
DIY

A Summer Survival Guide for DIY Boat Lift Care

August 19, 2025
3.4k
running shot of Marlow Avalon 65
Boats

Inside the Bold New Marlow Avalon 65 Yacht

August 18, 2025
3.5k
Bill Healey smiling
News

Passing of a Legend

August 15, 2025
53.5k
Man on the bow of his boat controlling his docking with a remote
Electronics

How Remote Docking Systems Boost Safety and Makes Every Trip Effortless

August 15, 2025
3.4k
Young boy with grandfather catches fish on the beach
Fishing

How to Get Kids Excited About Their First Fishing Adventure

August 15, 2025
3.3k
Facebook Instagram TikTok Youtube LinkedIn

Navigation

  • About Us
  • Advertise
  • Subscribe
  • Careers
  • Contact Us
  • Terms Of Service
  • Privacy Policy
  • Manage My Subscription
logo

1591 E. Atlantic Blvd, 2nd Floor
Pompano Beach, FL 33060
Office: +1 (954) 522-5515
Fax: +1 (954) 522-2260
Contact us: info@southernboating.com


Newsletter

* indicates required

© 2025 Southern Boating & Yachting, INC.

No Result
View All Result
  • Boats
    • Center Consoles
    • Dual Consoles
    • Motoryachts
    • Power Cats
    • Sport Cruisers
    • Tenders & Ribs
  • Destinations
    • Regional Reports
    • Bahamas
    • Caribbean
    • U.S. Atlantic
    • U.S. Gulf
  • Engines
    • Engine Buyers Guide
  • Maintenance
    • DIY
  • Electronics
  • Lifestyle
    • News
      • Boating Log
    • Fishing
    • Food
      • Drinks
      • Appetizers
      • Entrées
      • Dessert
      • Holiday
  • Gear
  • Shop
  • Digital Edition
  • Advertise
  • Subscribe

© 2025 Southern Boating & Yachting, INC.

  • About Us
  • Advertise
  • Subscribe
  • Careers
  • Contact Us
  • Terms Of Service
  • Privacy Policy
  • Manage My Subscription
  • About Us
  • Advertise
  • Subscribe
  • Careers
  • Contact Us
  • Terms Of Service
  • Privacy Policy
  • Manage My Subscription