Common Questions About Boat AC Units

How much does a boat air conditioning unit cost?

There are many variables that make it difficult to give precise estimates for marine air conditioning unit installations for boat owners. To install marine air conditioning on a boat that doesn't have it today, you'll need to drill for both raw water intake and discharge. You'll also need to install a condensation pump, new shore power, new circuit breakers, run all the ductwork, install air returns, air vents and a thermostat. You can see more details here on how to do DIY marine AC installation.

A good rule of thumb is that a professional high quality marine airconditioner installation is usually between 5 and 10 times the cost of the unit itself. There really aren't airconditioning retrofit units or retrofit kits available for most units as technology and vendors have changed quite a bit.

Replacing an existing AC unit can vary from 2-5 times the cost of a boat ac unit depending on how many components need to be replaced or reinstalled.

How long does it take to install marine ac?

For most customers, BoatAC.net can install marine air conditioning and have your boat ready to go within 1-2 weeks. We also offer emergency service if you’re on a tight timeline.

If you have an existing system, we can usually replace it while the boat is in the water. If you don't have AC and want it installed on your boat, you'll need to have the boat out of the water to install the through hull(s).

Should I fix my Dometic Cruisair SMX or replace it (or my Marine Air Systems or Cruisair Marine AC unit)?

Most marine air conditioning units last around 10 years. In most cases, replacing something like a condensing unit or condensing coil can cost as much as replacing it with a new unit. New units operate as reverse cycle marine heat pump air conditioners - using unlimited sea water to improve energy efficiency.

Generally, if your circulator pump is running and your compressor is on and you don't have cold air or a frozen coil, your unit doesn't have refrigerant and will probably cost more to fix than to replace. A frozen coil means that you likely have an airflow problem - which is probably related to a dirty filter or other obstruction.

How do you size a marine air conditioner?

Marine air conditioning sizing is a bit complicated. In order for your unit to operate efficiently, you need to have the right size return and vents for the power of unit you have. If your unit has too much power for the amount of airflow, the coils can actually be damaged or even freeze! You can have similar problems with overheating without proper water flow.

Please give us a call and we can help you design the right marine air conditioning system for your boat.

I have a Cruisair marine air conditioning unit or a Marine Air Systems unit that I’d like to replace, but I can’t find a similar model online. Do you have any of those units?

After Dometic acquired Cruisair, they updated the designs on most models. They aren’t identical and take many modifications to fit the same connections.

However, we have a lot of experience updating Cruisair split systems to new self-contained systems and are able to reuse many of the components. We don’t recommend trying this yourself unless you have a lot of HVAC and marine repair experience.

What is the best marine ac unit for my boat?

There are a number of good vendors today. We prefer Marinaire and Mabru Power Systems for most customer installations. They are quiet, durable and efficient. Check out our choosing the best marine air conditioner page.

How do I prime my boat AC system to get water flowing?

Generally, once you've opened up the main valve, water should fill your system or be available to replace the marine antifreeze that you may have in your system. If you turn on the AC system and don't see water coming out, the most likely cause is some air trapped at the top of the strainer cap.

To fix this, turn off your AC system. With the through hull valve closed, check the strainer basket for any debris and clean it. Next, with the strainer cap off, open the through hull valve - while ensuring that you'll be able to quickly close it.

You will probably see water start flowing out of the strainer. As soon as you do and any air bubbles are gone, close the through hull valve and replace the strainer cap. Make sure you're careful with the threads - you don't want to strip them. Then, reopen the valve and turn on the marine ac unit again.

If the water still isn't flowing, we suggest giving us or another marine mechanic a call. It is likely that there is debris stuck somewhere in the system. We come to each service call with compressed air, powerful vacuums and special fittings to be able to clean out any debris and get your boat AC system running again.

Also, watching our de-winterizing video may help as well (this link jumps right to the strainer part of de-winterizing).

I just turned on my marine air conditioning unit for the first time this season and it shut down. What’s going on? Can you help me with troubleshooting boat AC to make my air conditioner work?

There are many safety features in marine a/c units to prevent leaks, overheating or other problems. In newer devices, the thermostat may show a code like P3, P4 or PS (looks like P5). Typically, those codes indicate leaks in refrigerant, insufficient water flow or obstructed airflow. Unfortunately, it can be very time consuming to properly diagnose root causes and often costs as much to fix as to replace.

Can BoatAC.net replace my Marine Air Systems "split system” with a self-contained unit?

Yes! We can replace your existing split system with a new self-contained marine air conditioning unit from Marinair Marine AC or Mabru Power Systems.

What does a LO or LO / AC error on my marine air conditioner mean and what causes it?

Marine air conditioning units are very sensitive to fluctuations in electrical current. They need to be provided with consistent voltage and amperage to function appropriately. As a result, most modern marine ac units will shut down automatically when they detect the wrong voltage or other irregularities in the electricity coming to them.

There are myriad issues that can cause this such as corrosion of wires, grounding problems, too much load on your boat’s electrical system or internal electrical component issues.

What do Hi PS or Low PS error messages on my marine air conditioner mean and what causes them (btw, PS often looks like P5)?

Both refer to the pressure in the compression system in your marine air conditioner that creates the cooling effect that ultimately cools the air blown into your cabin. Low pressure usually indicates a leak - which could be too small to be seen with a naked eye. High pressure usually means that there is an issue with the flow of refrigerant through the system.

This can result from blockages or kinks in hoses, damaged coils or similar issues. Unfortunately, both of these tend to be very time consuming to diagnose and resolve. We strongly recommend against adding more refrigerant to a marine air conditioner that is known to leak.

Even small leaks often grow quickly and could damage your unit or even cause more serious issues.

What does PE (Program Error) on my marine air conditioner display mean and what can I do about it?

PE stands for program error and means that there is a software problem inside the electronics that control your marine air conditioner. Your unit will likely shut down in response to this error.

Often, these errors require a professional diagnostic, though some boat air units may allow you to swap out the electronic components. In some cases, these errors may also be caused by other issues that the system hasn’t properly diagnosed.