General Boat Information

The singularly most misunderstood, but frequently discussed, problem in boating is corrosion. Corrosion of metal components below the waterline will be a problem all boaters will eventually encounter and inevitably discuss with their boating neighbors. By far, the best source of information is a specialist such as a marine electrician, electrical engineer or metallurgist. Unfortunately most of them speak an incomprehensible language. Furthermore, the few specialists who are able to speak in simple, understandable terms don’t stop in time. They continue their explanations about ions, electrons and current carrying conductors until the basic explanation gets lost in the mental overload that follows. For those who wish to understand this subject in basic terms, you are in luck. The following explanation is written by an electrical simpleton and remains basic from start to finish.

Let’s begin with some very basic concepts. Alternating current (AC) is the type of electricity from the shore power cord, generator or alternator. Direct current (DC) is the type of electricity from the batteries. Circuit breakers are designed to prevent the overheating of wires and fires. Ground fault circuit interrupter devices, such as G.F.C.I. protected AC electrical outlets are designed to protect people. It is more important to protect people and prevent fires than it is to prevent corrosion. Bonding is connecting metal components with wires, resulting in electrical continuity. This is done with most below waterline metal components, including through hulls, struts, propeller shafts and rudders.

Testing for voltage and current can get complicated fast. The only testing we will discuss is electrical continuity. On virtually all electrical meters there is a continuity test, the symbol is an ohm sign (horse shoe). To determine if one metal component has continuity to another, set the tester on this setting, touch one metal with one of the tester’s leads and touch the other metal component with the other lead, continuity is indicated by a beep or a number. A number near one is good continuity. This test will allow you to determine if your rudder is continuous with a sacrificial anode or if a through hull is included in the bonding system.

It is unlikely that the cause of your corrosion problem is the “stupid wiring” at the marina. The wiring on your dock is almost certainly to an electrical code. The wiring on your boat is almost certainly not to code, as the only legal requirements apply to commercial, not recreational vessels. There is no “code” or Coast Guard requirements for the electrical system on your boat. While there are standards and recommended practices, compliance with them is voluntary. Regardless, metal corrosion in boats is a result of the laws of nature or a failure aboard the boat and rarely a result of a problem with the wiring on the dock.

The normally green AC ground wire used by the marina does provide a path for an electrical current that can contribute to corrosion. It also provides a path to ground in the event of an electrical problem and is designed to save lives. Don’t cut it! There are two common choices that can be used to allow the safety aspects of the AC ground wire and reduce or eliminate its contribution to corrosion, galvanic isolators and isolation transformers. Galvanic isolators are relatively inexpensive devices that prevent most problems associated with the AC ground wire. A more sophisticated, expensive and reliable method to prevent AC ground wire related corrosion is an isolation transformer. Without falling into the abyss of electrical theory, both devices reduce the potential for corrosion on your vessel. By using these devices and leaving the AC ground wire connected as designed, the boater can reduce or prevent corrosion while allowing the safety components to function as designed.

There are two primary types of corrosion experienced by boaters: galvanic and stray current. Galvanic corrosion is a natural process which occurs when dissimilar metals have electrical continuity and are immersed in the same electrolyte. In other words, different metals are either in contact with each other or connected by a wire and they are in the same body of water. This is by far the most common cause of corrosion. Stray current corrosion is caused by an electrical current leak and in the boater’s world is almost exclusively direct current (DC). This simply means that the primary source of the power driving this type of corrosion is your batteries not your shore power cord.

Another type of corrosion experienced mostly by high performance vessels is called cavitation corrosion or impingement. This primarily is seen on high speed propellers or rudders and is not addressed in this article. Anaerobic corrosion or oxygen starvation damage effects stainless steel where it is wet and starved of oxygen. Sailboat rigging and propeller shafts are common victims of this type of corrosion; this is also not addressed in this article. Both of these types of corrosion are unusual.

Galvanic corrosion is the common cause of corrosion on boats. The prerequisites, electrical continuity between the dissimilar metals and common water are the only things we need to understand to fight the good fight against it. If we bond all below waterline components, the least noble metal will corrode faster. While the theory is most easily understood if we use two separate pieces of metal in our examples, a single metal component can galvanically corrode. A bronze propeller is an alloy of several metallic elements, including copper and zinc. In this example, if left unprotected, the zinc will corrode out of the alloy, leaving a higher concentration of copper. This results in a pink color, versus bronze or gold. It also results in a much softer and weaker metal. Galvanic corrosion can also occur where two dissimilar alloys are in contact above the waterline, such as a steel fastener in an aluminum toe rail. In this case the aluminum will corrode. The least noble metal will lose this fight every time. This is a fundamental law of nature.

To protect against galvanic corrosion we use paint, sacrificial anodes (usually zinc), galvanic isolators or isolation transformers. The most effective form of protection is paint. If a piece of metal is completely isolated from the ocean by paint, it will not corrode. This is the initial method for protecting outdrives and outboard engines. The paint has to be designed for this purpose; anti-fouling paint is not designed to prevent corrosion. Metal boats are painted to reduce corrosion.

For a sacrificial zinc anode to protect a metal component from corrosion, it needs to have electrical conductivity and immersion in the same body of water. In other words your zinc anode must be touching or connected by a wire to the metal you are trying to protect and they both have to be on the bottom of your boat or in the same component in your engine. Simply speaking, connect all submerged metal to the zinc anode. The anode on your transom is not protecting your rudder unless your meter beeps when you touch both components. The sacrificial anode in the engine’s heat exchanger (a big round tube on the back of your engine) does not prevent corrosion in the exhaust manifolds. And, by the way, you should replace that anode in your heat exchanger.

The plate zinc on your transom rarely protects the propeller shaft and the propeller. It is difficult to maintain continuity with a propeller shaft that spins several thousand revolutions per minute. The most practical means to protect the propeller shaft and propeller from galvanic corrosion is a collar zinc installed directly on the shaft. You do not need to put a zinc anode on every piece of submerged metal. However, if you wish to provide galvanic corrosion protection, the metal does require continuity with a zinc anode located somewhere on the bottom of the boat.

By their nature, outdrives have corrosion challenges. Aluminum is low on the galvanic chart thus subject to corrosion more easily than bronze or stainless steel. Zinc anodes can reduce corrosion on an outdrive but the rubber bushings isolate the various components including the hydraulic rams, steering components and transom assemblies. Electrical continuity must be maintained between each component part and a sacrificial zinc anode in order for all parts to have protection. Small cables used for this purpose often become disconnected and the zinc anodes are more difficult to see and maintain than transom plates or propeller shaft collar zincs.

Trim tabs corrode. Deal with it.

Stray current corrosion is a much more rapid and damaging condition. The good news, it is unusual. The bad news, it is much more destructive and more difficult to diagnose. Extreme cases of stray current corrosion can result in a good propeller taking the form of Swiss Cheese in a matter of days. A through hull flange can disappear and solid steel components such as propeller shafts and rudder shafts can be severed. As previously mentioned, the root cause of this problem is a DC electrical stray current leak. An electrical short circuit has occurred and the current is being discharged into the water. One piece of metal will inevitably be coated with a white compound and another piece of metal will suffer metal loss. What the boater will experience is a sudden change in the condition of a submerged metal component, often found by a diver. The root cause will often end up being a failed electric motor, bilge pump or battery charger.

Sacrificial zinc anodes will not protect against stray current corrosion. Superman is defenseless against Kryptonite and metal is defenseless against a stray current. If a stray current problem is suspected, call a professional. The source must be eliminated. Take immediate action, boats have sunk after the through hulls were destroyed by stray current corrosion in a few days.

We do not believe that all metal components necessarily require bonding and protection with a sacrificial zinc anode. While there are standards which recommend this practice, we have seen many quality alloys last for several decades, virtually undamaged. We do believe that a bonding system should be complete if attempted, a complete bonding system or no bonding.

Fiberglass boats can not be “over zinced”, or install so much zinc that damage is caused. Wood and metal boats can be “over zinced”. This issue is particularly important to wooden boat owners. The amount of zinc installed on wooden and metal vessel is important and should be measured and maintained actively.

There are devices available to measure the amount of protection provided by zinc anodes. They are seldom understood or used as designed. If your boat has one, either learn how it works and use it actively or abandon it and use the simple system of bonding everything to a zinc.

There are more sophisticated corrosion prevention systems which are generally used in commercial applications. While zinc anodes are “passive” some outdrives and many steel ships and structures use “active” systems. Some of these systems impress a current into the water to prevent corrosion. These systems are beyond the scope of this article.

Corrosion of that toe rail we discussed earlier (and other above waterline metal) can be reduced by washing away the salts left after a day sailing. We won’t broach the subject of tank failures, just keep them dry.

Remember to protect metal with an anode; it needs electrical conductivity and a shared body of water. Sudden corrosion or significant changes in the metal components require immediate attention by a qualified expert, and follow the advice of that crusty boating neighbor at your peril.

I began my career as a marine surveyor in the specialized niche of a damage assessor. Christian & Company, Marine Surveyors Inc. continues to perform a large number of damage appraisals, working for marine claims departments, boat owners and boat yards. Heavy weather gives rise to an increase in damage claims, with most of the claims occurring while the vessel is in its slip or on a mooring. Based on our experience, there are a few, simple maintenance procedures, which will prevent most heavy weather related damage.

Anticipation and preparation for heavy weather is crucial. Just as most boaters secure loose items to prepare for a voyage, we must prepare our vessels for exposure to heavy weather. The intense rain fall in Southern California in the month of January magnified the problems with leaks.

Many boats have leaks through hatches, port lights or a myriad of hardware fastened to the deck. Many times just properly closing and securing these hatches, tightening the dogs and installing covers is sufficient. Occasionally all hatch gaskets, port light seals and even bedding compound requires maintenance. Water stains on the interior of a vessel are a sure indication of a leak above.

Some vessels accumulate a significant amount of water in the bilge during heavy rainstorms. Hatch drains are a common culprit if they are improperly maintained. A hatch drain plugged with dirt and debris prevents the drain from functioning and will allow the water to run over the lip of the drain and into the bilge.

Many trailer boats “sink” on their trailer. Canvas covers allow rain to pool and leak through. We handle “trailer submersion claims” every spring. Boat covers need to be maintained and installed with a camber, causing the water to run off the vessel and not accumulate on the cover. Drain plugs should be removed, the bow should be up and debris in the bilge should be removed to prevent it from “clogging the drain”. Trailer boats are no different that boats afloat, they need to be checked on periodically and after a heavy rain is a good time.

A trick of the marine surveying trade is to look below areas of water accumulation for problems, including problems with the coring, fungus deterioration, warping of plywood and mould.

Significant rain water accumulation in the bilge of the vessel can always be handled by a functional automatic bilge pump provided that a good power source is available. Bilge pumps and float switches should be checked. Batteries should be charged and chargers should be functional and utilized. While checking the function of bilge pumps, it is a good time to check the discharge systems. If any of the bilge pumps, sump pumps, or similar pumps are located lower than their discharges and the discharge is located below the waterline, the system requires a vented loop to prevent back flooding. Check valves should not be relied upon in this application. The bilge should be clean of debris that can foul the pumps.

Heavy weather also comes with increased winds and large swells. These forces test the lines which are securing vessels. Owners are responsible for portions of their mooring arrangement and most boaters are responsible for their dock lines. Heavy weather requires lines to be checked for chafe, chafe protection to be properly utilized and fenders to be checked and positioned properly.

Absentee owners should engage the services of a maintenance company or a trusted boating friend. Checks should be made before and after all heavy storms. Water leaks or water accumulation should be dealt with preemptively. Bilge pump function, drain systems, covers and the proper securing of lines can be quickly assessed and by doing so much of the damage we see can be prevented.

Insuring a boat against damage is wise. Realize that not all damage is covered by insurance. Long term leaks can lead to coring deterioration, wood rot, mould and mildew and this type of damage may not be covered by insurance. If your vessel is damaged by another vessel which comes loose during a storm, the liability adjuster for the other vessel may decline coverage based on an exclusion for an “act of god”. Having your own insurance will cover you in this instance. The tsunami caused by the Chilean earthquake broke a dock by the Bali Hai restaurant and two boats were separated from their mooring in America’s Cup Harbor. The January storms contributed to the escape of many boats from their moorings.

After the rains subside the vessel should be opened and ventilated. Wet cushions should be lifted and allowed to dry. Fungus deterioration of wood requires wood, proper temperature range, fungus spores and moisture. The only one of those four prerequisites that is under the control of most boat owners is moisture. Properly ventilating the vessel after a rain storm will also prevent mould and mildew.

Sailboats need to consider if the sails are properly secured. Walk through a marina during a storm and you are sure to see a couple roller furling jibs flogging in the wind. Powerboats should consider their canvas as well. Is the canvas or enclosure properly secure? Is the external upholstery secure? Is the tender secure and covered to prevent water accumulation?

We hope this is helpful and informative and will assist in reducing damage to your boat, but if not, perhaps we will have the opportunity to spend some time with you. Please keep Christian & Company Marine Surveyors, Inc. in mind for any future marine surveying needs of yours or your boating friends.

 

This article was edited on March 1, 2016.

Marine surveyors’ primary product to the boating community is a vessel condition and valuation report. By default marine surveyors have become the de-facto vessel appraisers in the United States. Due to the falling value of vessels, Christian & Company has received numerous requests for appraisals in order to lower the basis for property tax assessment. As a result, we did some research to educate ourselves and to share what we learned with others who may be interested.

In California there is a state personal property tax of 1% per year. The research we did was primarily through the San Diego Tax Assessors office; they are extremely helpful. They appraise vessels and assess taxes, which include the 1% state personal property tax and may include slightly more taxes depending on geographic location for items such as retiring bonds. The additional localized taxes seldom are more than .2 percent. The address for the San Diego marine and aviation tax assessor’s office is 9225 Claremont Mesa Blvd. 1st Floor, San Diego, California 92123. Phone numbers for San Diego, Orange County, Los Angeles and Ventura counties are included at the end of this document.

All vessels located within the county on January 1st of each year are subject to the tax. A list of all vessels registered in the state of California is provided to the tax assessor’s office by the California Department of Motor Vehicles. The DMV does not collect the property tax on vessels; it is collected by the County Assessors office. Marina operators provide a list of slip renters and the assessors office has a team of four who “walk the docks”, collecting information on vessels to supplement the information provided by marina operators. This is the method for obtaining a list of U.S. documented vessels that are subject to the tax.

When the vessel first appears on the tax assessor’s roll, it is appraised. The assessor appraises the value as of January 1st of each year. The initial value may be determined by the purchase price or through appraisal techniques. Among tools available and used by the assessor’s office are value guide books including A.B.O.S., N.A.D.A. and B.U.C. and value data bases available on the internet. Due to the number of vessels which require appraisal and the limited personnel, the value of an individual vessel is not thoroughly and extensively researched by the tax assessor’s office and vessel inspections are not performed. They appraise thousands of vessels and thus are unable to spend too much time on each appraisal.

After an initial value of a vessel is established, the subsequent value is adjusted annually per a depreciation scale determined by the tax assessor’s office. A higher depreciation percentage is applied to new vessels and the percentage of depreciation decreases with age.

Based on our experience, vessel values have suffered a significant decrease in the last two years and are currently trending rapidly downward. We recommend you take a few moments to review the appraised value of your vessel and feel free to call or email us if you would like a free verbal approximation of its value. Perhaps a formal appraisal of your vessel will allow a reduction in taxes for the immediate tax bill and for years to come.

The tax assessor’s office has no firm or written guidelines as to what they will accept as proof of value for your vessel. There is a handbook available through the State Board of Equalization. A marine survey is one of the options available for you to document the current value of your vessel. The tax assessor’s office will consider any documentation and if they agree, they will change the appraised value and the tax accordingly. If they disagree with your value an appeal can be made. Appeals are initially addressed with a second consideration of the value and are followed with a board review if the vessel owner and the assessor’s office still disagree on valuation.

Christian & Company Marine Surveyors, Inc. would be happy to provide a written valuation of your vessel and our fee is often less than the tax savings in a single year, with additional financial benefits in the years to follow.

County Tax Assessor – Marine and Aviation contact telephone numbers:

San Diego 858-505-6200

Los Angeles 213-974-3119

Orange County 714-834-2772

Ventura 805-654-2193