When you are out on the water, comfort matters just as much as safety. After a day of fishing, swimming, or sailing, having hot water for a shower, cooking, or cleaning makes life on a boat far more enjoyable. Traditional marine water heaters can be bulky and slow, storing a limited amount of water that runs out quickly. A tankless water heater solves these issues by heating water on demand, giving you a constant supply without wasting space.
In this guide, we will start with the top tankless water heaters for boats in 2025, then move into a full buyer’s guide so you know exactly what to look for.
Top Tankless Water Heater Picks for Boats
1. Rinnai V65EP Tankless Water Heater
Known for reliability, the Rinnai V65EP runs on propane and delivers up to 6.5 gallons per minute (GPM). While it is often used in homes, it adapts well to larger boats with high water demand. Its compact design and venting flexibility make it suitable for marine installation when properly protected from saltwater exposure.
- Best for: Large boats and yachts with multiple fixtures
- Pros: High flow rate, excellent temperature stability, long lifespan
- Cons: Requires more installation space than small marine units
2. PrecisionTemp Marine RV-550NSP
This propane-powered heater is built specifically for RVs and boats, with stainless-steel components to resist corrosion in marine environments. It provides around 1.5–1.6 GPM, perfect for smaller boats or single-use hot water needs, and features freeze protection.
- Best for: Small to mid-size boats
- Pros: Corrosion-resistant, compact, efficient
- Cons: Not designed for heavy simultaneous use
3. Camplux 2.64GPM Outdoor Portable Tankless
If you want a portable, flexible option, the Camplux propane heater is lightweight and easy to mount on deck or store when not in use. It delivers up to 2.64 GPM and works well for deck showers, rinsing gear, or cooking needs.
- Best for: Fishing boats and weekend cruisers
- Pros: Portable, affordable, high flow rate for size
- Cons: Needs weather protection in marine use
4. Eccotemp L5 Portable Tankless Water Heater
One of the most popular portable units, the Eccotemp L5 is small, easy to store, and delivers 1.5 GPM — enough for quick showers or rinsing gear. It runs on propane and connects to a standard garden hose fitting, making it simple to use on boats with basic water setups.
- Best for: Smaller boats and occasional use
- Pros: Lightweight, affordable, easy setup
- Cons: Lower flow rate than larger units
5. Bosch Electric Mini-Tank Tronic 3000T
For boats that spend most of their time docked with shore power, this compact electric water heater is an option. While not a true tankless model, it heats water quickly on demand and stores a small amount for instant use, making it ideal for quick tasks like washing hands or small loads of dishes.
- Best for: Docked boats with steady shore power
- Pros: Easy installation, no propane needed, quick recovery time
- Cons: Limited hot water supply for showers
Why Tankless Water Heaters Are Great for Boats
Boats have limited space and weight capacity. A tankless system removes the need for a large storage tank, freeing up space while giving you hot water whenever you need it. They are also more energy-efficient since they only heat water on demand.
- Compact and space-saving
- Endless hot water when fuel or power is available
- Lower fuel or electricity use compared to tank systems
- Reduced maintenance — no tank to clean or replace
What to Consider When Choosing a Marine Tankless Water Heater
Fuel Type
Propane is common for off-grid marine use, while electric models work well for boats with reliable shore power or generators. Diesel-powered heaters are another option for some marine setups.
Flow Rate (GPM)
The right flow rate depends on how many fixtures you plan to use at once. Small boats may need just 1.5–2 GPM, while yachts with multiple bathrooms may require 5+ GPM.
Corrosion Resistance
Saltwater environments are harsh on equipment. Look for stainless steel or marine-grade materials to resist rust and corrosion.
Ventilation and Safety
Propane units require proper ventilation to avoid carbon monoxide buildup. Marine installations often need specialized venting to prevent seawater intrusion.
Size and Weight
Measure your installation space and consider the unit’s weight, especially for smaller boats with limited carrying capacity.
Installation Tips for Boats
- Install in a dry, well-ventilated compartment
- Use marine-rated fittings and hoses
- Ensure propane systems have proper regulators and safety shutoffs
- For electric models, verify shore power or generator compatibility
- Protect portable units from salt spray and rain when in use
Maintenance Advice
Marine environments require more frequent checks due to salt and moisture:
- Rinse the exterior of portable units with fresh water after use
- Inspect for corrosion or loose fittings regularly
- Flush the system to remove mineral buildup at least once per season
- Check fuel lines and electrical connections before long trips
Conclusion
A tankless water heater can make boat life much more comfortable. For larger vessels, the Rinnai V65EP offers high capacity and durability. For smaller boats, the PrecisionTemp Marine RV-550NSP is a compact, corrosion-resistant choice. The Camplux 2.64GPM and Eccotemp L5 are portable options that work well for deck showers or occasional use, while the Bosch Tronic 3000T is ideal for docked boats with shore power.
Choose the model that matches your boat size, power source, and usage habits, and you will enjoy hot water on board without sacrificing space or efficiency.