Salt and brackish water:  Just how harmful are they to antique and classic boats?

by Judy Hills, Roving ACBS reporter

Those ACBS Chapters that put on shows where the water is salty or brackish may have a hard time convincing ACBS boat owners to show their boats in the water because of their fear of the harm that it may do.  This article is intended to present information on the effects of salinity on boats, engines, trailers and accessories and assumes that the boat in question is not regularly run in brackish or salt water.  This article addresses trailered boats, not larger ones that require a berth.  The longer the boat is kept in that type of water, the greater the risk of encountering problems if proper care is not taken.

Let’s start with the basics.  What is salinity and how is it measured?  Salinity is the measure of all the salts dissolved in water. It is generally measured in parts per thousand (ppt).  The average ocean salinity is 35 ppt and the average river water salinity is 0.5 ppt or less. (  


Hills’ Sea Skiff at Beaufort, NC show. It is in salt water. We were the only trailerable antique and classic boat shown in the water.


The salinity of brackish water (seawater mixed with fresh water) is somewhere in between those two measures and will mostly depend on how close the river or other body of water is to an inlet from the ocean.  Low salinity is considered less than 1 ppt.  According to the National Ocean and Atmospheric Administration (NOAA), the salinity of brackish water can change from one day to the next depending on the dilution by stormwater runoff, tides, weather and other factors.

So, the first thing you need to determine is the salinity of the body of water where the boat will be used.  If the show site is near an ocean inlet, you can pretty much assume that the salinity of the water will be close to 35 ppt.  An example of this would be the Beaufort, NC Wooden Boat Show.  This event is held on Taylor’s Creek very near the Beaufort Inlet (Atlantic Ocean). 

The Raleigh Durham Chapel Hill Triangle Chapter of the ACBS holds their show in New Bern, NC which is on the Neuse River.  The water in that area is brackish and averages a salinity of 4.7 ppt yearly, but during the month of the show (May) it averages 0.6 ppt. 

How can you determine the salinity of a given body of water?  In some rivers there are programs that track salinity.  The best source of this information would be the Rivekeeper.  There are Riverkeepers in most areas. Use Google to type in the name of the body of water and type in the word Riverkeeper.  If you are the show organizer, you should research this and add the findings to the information on the show.  Here is an example from the New Bern show:

Salinity: For those concerned about the salinity of the brackish water of the Neuse River, in an average year the salinity in the New Bern area runs from 0.0 parts per thousand (ppt) to 4.7 ppt. Salinity runs from 0 ppt in fresh water to about 30 ppt in full strength sea water. The average salinity for May in the area is 0.6 ppt. Low salinity is 1.0 ppt or less.  Any number of factors can affect the salinity on any given day. Per the Lower Neuse Riverkeeper, one great resource for this data is UNC’s MODMON program. Here’s a link:  What you’re looking at on the linked page reads left to right with the left side of the chart starting upriver of New Bern and traveling down river as you read to the right. The salinity is the top banner of the chart. Station number 30 (reading the numbers across the top of the chart) is center of the Neuse right at Bridgeton Harbor Marina. Generally speaking, the highest readings are bottom waters but the surface waters at that spot very rarely get above 2 ppt. If you are really concerned about this issue, we suggest you display your boat on a trailer.

In making the decision, knowing the salinity is only the beginning.  How long will the boat be in the salt or brackish water?  The length of time the boat sits in the water and the amount of use it gets in that same water are additional factors.  Generally speaking, most shows are less than three days so that is not really much exposure.  What type of hull do you have?  Aluminum boats are more prone to galvanic corrosion in salt water.  Does your engine have an enclosed cooling system (newer technology)?  If yes, you have one less thing to be concerned about?  Is your trailer aluminum?  Aluminum trailers fare better in salt and brackish water than other types. 

There are many online forums about using boats of all types in salt and brackish water.  You’ll see everything from “don’t ever do it” to “it’s OK as long as you meticulously decontaminate the boat” to “don’t worry about it.”  These forums are for the average boater regularly using the vessel in those types of water and don’t address the concerns of those owning antique and classic boats.

Boats that are stored on trailers and are only left in the water for short periods of time really don’t need bottom paint—a good coat of wax and regular cleaning will result in a clean hull—no matter what type of water you boated in.  Once you have applied bottom paint, you can’t go back—unless of course you sand the hull down and start over.  It has been said that copper bottom paint turns green in salt water.  In researching this topic we did find a reference that said, “Many of the older bottom paints with very high copper content turned green after a few months” in salt water.  Research the paint you used on your boat’s bottom for guidance on this issue.

boating on the Bayou photo by John Thompson

Lengthy use in salty water has the capability of ruining trailers, risers, manifolds, engine mounts, and steering cables.  It will rust screws and accessories that are not brass or stainless steel.  It will pit aluminum.  This list is not intended to be all inclusive, but you get the picture.

So let’s assume that you determine that the risk of damage to your boat at the show is low because the boat will be in brackish water with low salinity for less than 48 hours.  You decide to show your boat in the water.  How should you take care of the boat, engine and trailer?  More elbow grease will be needed if sea conditions were such that the boat was exposed to wave action and overspray.  Since you are not at home, your options for care may be somewhat limited.  If there is a water source available at the ramp, hosing off your trailer should be sufficient.  If the interior got wet, wipe it down with the appropriate solution and dry it (cushions, fixtures, dash, etc.).  Spray the boat hull down and scrub with a soft brush and mild detergent.  Rinse and wipe dry with a clean cloth, paying special attention to chrome fixtures. 

Now that you have dealt with the boat’s exterior, it is time to address the engine.  Here is the “old school” way to flush the outboard engine if the engine was used in salt or brackish water.  If you don’t already have one, purchase a flush muff from a marine dealer.  Connect to a garden hose, fit the muffs over the engine’s water intakes on the sides of the gear case, turn the water on, start the engine and let it run for five or ten minutes. More modern engines have standard built-in garden hose attachments and some should not even be run when flushing so carefully read the manual for your engine. All manufacturers make a statement about ensuring that all water is drained from the engine after flushing.  To read more on this topic, access this URL:  Another method has the owner using a “Fake-A-Lake” which allows for safe engine operation of your boat while on land or on the trailer.  This apparatus allows you to flush, tune or winterize an inboard engine out of the water. The rubber cup creates a dependable seal on most hull shapes. 

“Last Nickel” 1947 Chris Craft U-22 owned by John Justice.

Ideally, you should clean the boat and flush the engine as soon as the boat is back on the trailer, but given conditions at the boat show, this may have to wait.  Do both as soon as feasible.  John Justice of the RDC Triangle ACBS Chapter offers this final advice, “I consider short-term use very different than constant exposure.  I’ve used Last Nickel (a 1947 U-22 Chris Craft) in salt, brackish and fresh water.  There is an additional precaution that some of us take to keep the engine completely flushed—we go boating in some fresh water!” 

Boat shows are more fun when the boat is in the water and used during the show. If you follow these simple guidelines, you should not experience problems.  The show organizers appreciate owners that show their boats in the water and give rides to the public.  Take the plunge!


1 Comment

  1. In short….
    Fresh water rots wood
    Salt water rots ferrous metal
    But both take time
    Short exposures to salt water followed by washdowns are harmless
    Gene Porter

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