Retrofitting a catamaran like the 2008 Lagoon 420 for air conditioning is a significant project that transforms the vessel into a true four-season cruiser. Since your Lagoon wasn’t originally equipped with A/C, this “clean slate” installation requires careful planning for ducting runs, structural bulkhead penetrations, and a robust raw water cooling system to handle the combined 32,000 BTU load.
At Yes Centers, now located at our new facility at 1207 Marina Bay Drive, we specialize in complex marine HVAC retrofits for boaters in Kemah and the surrounding 30-mile radius.
The Anatomy of a Lagoon 420 A/C Retrofit
Installing three self-contained units on a catamaran involves more than just mounting the boxes. Here is how we approach a full-scale retrofit for a boat in the Clear Lake and Galveston Bay area:
1. Plumbing & Raw Water Systems
To support two 10k BTU units and one 12k BTU unit, you need a high-volume, reliable cooling source.
Pump & Strainer: We would typically install a high-capacity magnetic drive pump (like a March or Dometic PMA series) to provide sufficient head pressure for all three units.
Through-Hulls: This requires new bronze through-hull fittings and seacocks. We ensure these are properly bonded and sealed to ABYC standards.
Manifold System: A custom manifold is often needed to split the raw water flow evenly between the three units to ensure consistent cooling across the hulls.
2. Structural Ducting & Bulkhead Cuts
Catamarans present unique challenges for ducting.
Bulkhead Penetrations: We carefully plan cuts through bulkheads to maintain structural integrity while ensuring maximum airflow.
Insulated Ducting: To prevent condensation and “sweating” in the humid Kemah air, we use high-quality R-value insulated ducting.
Grilles & Plenums: We source and install high-velocity supply grilles and return air plenums that match the Lagoon’s interior aesthetic.
3. Dedicated 30-Amp Electrical Circuit
Running 32,000 BTUs requires a dedicated power source to avoid tripping your existing house breakers.
Second 30-Amp Inlet: We install a new stainless steel shore power inlet and a dedicated A/C distribution panel.
Marine-Grade Wiring: All wiring is sized for voltage drop over the length of the catamaran’s hulls to ensure your compressors get the “clean” power they need to start under load.
Get Your Retrofit Started in Kemah
Yes Centers provides the professional boat yard services needed for this level of installation. Whether your Lagoon 420 is currently at Watergate, South Shore, or Waterford, you can bring it to our facility for the duration of the project. We serve the entire Kemah, Seabrook, and League City area.
For a detailed quote on parts (pumps, hoses, ducting, grilles, electrical) and labor:
Visit Us: 1207 Marina Bay Drive, Kemah, TX 77565
Call Us: +1 281-538-9377
Service Area: Every marina within a 30-mile radius of Kemah.
