How Long Can A Boat Stay In Saltwater Without Bottom Paint?

The growth of organisms on the bottom of a boat is a permanent issue that all boat owners must contend with. After a weekend on a lake, even hauling out will require the bottom to be cleaned and washed before storage. Boats that are always removed from the water and trailered to storage will not require bottom paint.

Even the finest gel-coat hull finish will provide micro-organisms living in the water with an ideal place to latch onto and start growing. Boats that will spend more than a few days in the water before being hauled out will require the hull to be treated with a biocide to minimize growth.

Soft algae growth will start forming on the hull of your boat within hours of going to water. Just below the waterline, the effect of the sun will encourage green algae to take hold of the boat’s hull. Other creatures will also find the algae irresistible, and hard growth such as barnacles will appear after two weeks in the water. Let’s look at some ways to avoid the use of bottom paint.

Why Some Boat Owners Dislike Bottom Paint?

The amount of drag created by the application of bottom paint is why some boat owners dislike having bottom paint applied to their boats. Some boat owners also claim that the bottom paint spoils the aesthetic of their boat.

Bottom paint is not required for the weekend speed boating enthusiast or owner of a sailboat that can be trailed to storage. Bottom growth is not an issue if the boat spends less than 48 hours in the water before being hauled out, cleaned, and taken to storage.

For these owners for whom optimal performance is a key issue, they will clean and polish the bottom of their boat and never allow algae growth to mar the performance and appearance of their boats. These boats will always have clean bottoms if their owners so desire.

For boats spending an entire season or year in the water, the growth on the bottom of their boats is a reality that has to be managed to maintain their speed through the water and the boat’s appearance

The condition of the water greatly influences the rate at which the bottom of a boat becomes infected with micro-organisms. The dirtier the water, the faster it grows. The waters in marinas, harbors, and lakes often contain a high concentration of organisms and conditions in which they flourish.

Some boat owners claim that bottom paint on a boat is a sign that the boat was poorly cared for and thus adversely affects the boat’s resale value. This is not true as modern bottom coating systems have been developed to optimize boat speed and hull condition.

Ten Tips About What Type Of Bottom Paint To Use

If you have become tired of cleaning and scrubbing your boat, get rid of it or get help. Antifouling paint or bottom paint has developed in leaps and bounds in recent years, and you are no longer limited to just four colors. Modern antifouling paint systems can come in any color that you fancy and make the ownership experience more rewarding.

Before deciding on which paint to buy, consider the following ten questions:

1. Does Your Boat Have An Aluminum Hull Or Drive Hardware?

Antifouling paints containing cuprous oxide will result in galvanic corrosion that can damage your aluminum hull or aluminum drive hardware. You need to select an antifouling paint that is zinc-based or contains a non-metallic biocide like ECONEA.

Alumaspray Plus and Hydro coat ECO are examples of paint systems compatible with aluminum hulls and sail drives.

2. Bright Colors Are Available. What Do You Want?

Paints containing white copper(cuprous thiocyanate), zinc, or ECONEA as a biocide can be formulated in colors ranging from brilliant white to brightly colored hues available from Pettit’s Vivid and Interlux Trilux 33. These white copper formulations require 50% less copper than the much heavier conventional antifouling copper formulations.

ECONEA is an excellent choice of biocide as it is metal-free and thus only 10% as heavy as cuprous oxide-based paints. The ECONEA also does not cause discoloration in the presence of sulfides (in sewerage water) as metal-based paints do.

3. Are You In An Area Where Copper Biocides Are Restricted?

Some marinas and marine areas prohibit using copper-based biocides due to their detrimental effect on the environment. Zinc or ECONEA formulations are the answer in such areas. Propspeed is a specialty bottom paint that contains no biocide and functions through the super slick surface that it creates. The water movement over the hull and through the propeller is enough to shed any growth off the surface.

4. Are you in an area where slime growth is a problem?

In waters where the water quality is such that algae slime growth on the hull is a problem, a bottom paint formulation containing Irganol is effective. Irganol disrupts the process of photosynthesis and is thus effective in controlling the growth of waterline beard.

Micron Extra or Hydro coat SR are two formulations that contain Irganol and are ideal for boats that reside in waters where slime growth is a problem.

5. Hauling out for winter, not repainting before splashing?

The solution to not applying bottom paint every year after hauling out for the winter is to select a co-polymer ablative antifouling formulation. The surface of the hull is cleaned off during water movement over its surface. Like a bar of soap, the coating will slowly wear off as the hull moves through the water, preventing any growth from taking hold.

When the boat is hauled out, the paint remains effective and requires light sanding before the boat is splashed again. This type of paint can be blended with ECONEA to form environmentally safer co-polymer ablative paints that will save a lot of time getting the boat ready for the new season.

6. Vinyl Based Paints Only Want Vinyl Based Surfaces

If your hull is made of vinyl-based esters, you will have to use vinyl base paint to adhere to it. 

7. Saltwater Vs. Freshwater – where does the boat live?

You will require a different bottom paint formulation depending on whether your boat will reside in salt or freshwater. Freshwater formulations will not work in saltwater. Determine where your boat will be operating the most and paint accordingly. Ask other boaters and bottom paint specialists in your area what they recommend.

8. How frequently will you use the boat?

If you use your boat a lot during the season but haul out for winter, co-polymer ablative paint is the best. If your boat is in the water year-round and only comes out for inspections, then high copper content epoxy paint is your best solution.

If you are a weekend boater, you can forgo the need for bottom paint altogether and rely on your discipline in cleaning the boat after every weekend. 

9. Do you store the boat out of the water when not in use?

Co-polymer paints offer the best multi-seasonal protection for boats hauled out for winter or during periods when not in use. As long as the coating thickness remains sufficient to see you through another season, you are good to go. These paint systems are more expensive, but their cost has to be compared to the time and expense of numerous haulouts and bottom paint applications.

10. Are you painting over old paint?

Never use new paint over old flaky paint. Never apply new paint over surfaces that have been coated with vinyl or PTFE-based paints. Never apply hard paint over soft paint. These are the golden rules when planning to apply new paint. 

You may be required to strip down to the original gel coat layer and start from a good base than wasting good paint over bad. If done correctly, you can save yourself a lot of future work by working from a known substrate.


Bottom paint treatments are essential to boats that spend extended periods in the water. The initial bottom paint treatment cost and effort will determine your annual workload and cost for keeping the bottom of your boat in prime operating condition. 

It is worth consulting an expert to obtain the guidance needed to select the best bottom coat formulation for your boat. Preparation of the surface before applying the paint is crucial to obtain the most out of your bottom paint treatment.

Modern bottom paint formulations are available in all colors, from white to bright, and can be mixed to fit the conditions in which you will be using your boat. The water resistance caused by excessive growth can cost you more in additional fuel consumed or extra time on passage, and it is well worth investing in the correct bottom treatment for your boat.