Ask The Experts

Solutions from the BoatUS Tech Team

Photo of The gelcoat on a 24-foot Four Winns anchored along Pictured Rocks National Lakeshore in Michigan

Is My Gelcoat Damage Permanent?

I've scrubbed the freeboard and gunwale my 1998 Cruiser Yachts 3850 with a Scotch scrubber sponge (like for pots and pans) and 409 with bleach each spring, followed by applying a 3M rubbing compound with a buffer. This season the shine didn't last and I have discoloration at the water line (brown; boat is white). I'm worried I destroyed my gelcoat and am wondering how to assess the state of it. Is it gone? Does it need wet sanding? Does it need polishing (same as rubbing compound I think), followed by waxing to bring back the shine and protect the gelcoat?

Don Casey: Gelcoat is relatively soft, and for sure you did yours no favor by scrubbing it with a pot scrubber. The good news is that gelcoat starts out relatively thick, so it can tolerate quite a bit of abuse before it's unsalvageable. What the condition of yours might be I cannot say, but you need to stop using harsh abrasives and chemicals. Your boat is plastic, not stainless steel or cast aluminum. Waterline discoloration is typically caused by tannins and other contaminants in the water. If you've made your gelcoat more porous by the use of bleach, this type of staining happens more easily and becomes more difficult to remove. Removal often requires a specialized waterline cleaner, which typically contains acids. The last thing your gelcoat needs is acid attack, but you may be out of options. If your gelcoat hasn't been thinned beyond redemption by all of your earlier abrasion, you might extend its life by polishing it a final time with a very mild cleaner polish — not a rubbing compound — followed by a double application of a good paste wax such as Collinite No. 885. In the future just wash and wax: you've already done too much polishing.

If the brown discoloration isn't from staining, if it was there before you launched, you may have rubbed away so much gelcoat that you're seeing the fiberglass laminate behind. If that's the case, you can't save the gelcoat. The hull will have to be re-gelcoated — an expensive, labor-intensive process — or you're faced with painting the hull to restore the color and shine. More polishing will just make your situation worse, and waxing won't help the discoloration.

Let's Find That Leak

I'm having a problem with heavy leaking of water in the aft head on the port side. It appears to be coming from rain. I've caulked various places in that area, to no avail.

Tom Neale: Often the most difficult part of fixing a leak is finding it. On fiberglass boats this is especially problematic because liners, grids, and other internal components often lead the water away from the actual leak. A good way to locate a leak is to station someone below where you normally see the water. Then, with a water hose from the dock, have someone methodically run water (just use normal pressure without a nozzle) onto the boat in the vicinity of the leak, starting at the LOWEST areas and working up and/or forward (uphill from the leak). Wait a while before you move the hose to another spot because you want the water to have time to run to its destination inside, if it's coming in where you're squirting. Slowly use a process of elimination to find the leak source. When the person inside sees water, you've isolated the area. Windows are a prime spot for leaks to occur. Over the years, gaskets and seals wear. Also a boat will work and this may loosen joints here and elsewhere. If you have a highly suspicious spot such as windows, start there. Once you find the leak, the exact fix will depend upon the nature and location of the leak. It may be that sealant, new gaskets, or something else is needed, but that call can't be made until you know what you're fixing.

Never Too Clean

Don Casey's response in the December BoatUS Magazine regarding oil changes may have muddied the waters. Another source recommends adding a bypass filter to extend oil life and, based on regular lab analysis, extend change periods significantly beyond a year. My owner's manual recommends every 250 hours or annually. I have a trawler and could change oil several times in a year when I did extended cruising. Now I use the boat locally on the south coast of North Carolina and don't accumulate 250 hours a year. I change oil and both oil and fuel filters annually in the fall. Your answer addressed seasonally used boats and is probably appropriate for northern boats, laid up in the fall, often on the hard, unused for five to seven months. But the question was from Alabama, not a cold-climate state requiring extensive winter preparations, unless this is a lake boat in the Ozark mountains. I guess the best advice is to follow your manual and use common sense.

Don Casey: The questioner asked about seasonal use and, more important, the specific question was should he drain the engine and leave it empty until recomissioning. The answer to that is no, period. Beyond that, I tried to make the case that your oil can't be too clean. I'm unimpressed by environmental concerns; we should certainly conserve oil, but by burning less of it, not by scrimping on lubrication. For a boater running lots of hours, there's a financial incentive to extend the time between oil changes. But saving an oil change every other year seems penny wise and pound foolish. Also, much of the confusion comes from the differing requirements between diesel and gasoline engines. Diesels are hard on oil and regular changes are essential. Better filtering can certainly extend the life of the lubricant, but filtering doesn't remove acids, so even with a super filter, I wouldn't leave old oil in my diesel when it will be idle for a while. You're right, you can't go far wrong following the engine manufacturer's directions.

Greasy Bottom

My 28-foot Bertram was safe in a New Jersey boatyard for Sandy. However, the surge and spills from other sources coated the bottom paint on the windward side with a mix of diesel, oil, and fuel. It seems to have soaked into the layers of bottom paint. Can I just degrease the surface and repaint next season, or will I need to take extra steps to avoid any issues?

Photo of a man degreasing the bottom of a boat

John Adey: I had the opportunity to speak to several paint manufacturers at a recent trade show, and the common answer was degreasing. Using any commercially available solution that cuts grease and oil is fine. Two pros mentioned a light 80-grit sanding. No one recommended a full bottom-stripping job (whew!). I'd definitely do a light sanding. The yard I use talked me into this practice with every re-paint and I've had excellent results, worth the effort and the Tyvek suits. They also mentioned that this was similar to the Gulf oil spill and, depending on your paint manufacturer, you may find more info on their websites. I'm glad you and your boat made it through OK.

Premium Anodes?

Judging by the wide range of prices and weights for supposedly equivalent zinc anodes of the same type and shape, zincs are not created equally. What are the chemical differences that might explain this and what are the most important specifications to check with manufacturers?

Don Casey: The amount of oxygen needed to keep stainless free of corrosion can't be obtained by a dripping packing gland. Depending on the type of stainless you have, you may never have a problem. Higher-quality stainless shafts like Aquamet 22 are highly corrosion resistant and won't have a problem in a stagnant shaft tube, whereas Aquamet 17 is much more susceptible to crevice corrosion (pitting). The pitting I've seen comes from the lower-grade stainless with very long shaft tubes (4-6 feet). So, tighten the nut, it's not doing much good, and keep the bilge dry! Anodes intended for boat protection typically come in three general types: zinc, aluminum, and magnesium. Traditionally, zinc was for saltwater, aluminum for brackish or mixed use, and magnesium for fresh water. Recently, however, zinc anodes have become potentially villainous because they also contain small amounts of cadmium, a toxic heavy metal, which the decaying anode releases into the water. In response, anode manufacturers have developed some aluminum alloys that so far seem to be as effective as zinc in saltwater. These aluminum anodes also last longer, which may or may not be a good thing, depending on whether longer life equates to less sacrifice and, necessarily, less protection. In any case, I strongly suspect that all of us will be using aluminum anodes exclusively in the near future, with the exception of freshwater boaters using magnesium.

There are alloy differences in the aluminum anodes provided by different manufacturers, and even with zinc anodes I've heard anecdotal grumbling about some imported ones having an abnormally short life. I've had this experience but can't say whether the shorter life was due to the anode or the environment. I've never seen published specs that would allow informed discrimination. As long as the alloy is less noble in the galvanic series than the metals it's protecting, and you monitor its decay, it should perform as represented. Excepting the premium for these newer aluminum alloy anodes, which have been priced higher than zinc (but the difference is fading), I'd be disinclined to pay extra for "better" anodes.

A Manifold Gamble

I usually replace my exhaust manifolds and risers on my Bayliner's V8 every five years, but some of my seasoned boating buddies say that this is a waste of money, that these manifolds and risers are good for at least one acid boil-out to remove clogs, scale, and other crud from the water passages. They say they should be as good as new after the boil-out and good for another five years. The walls are thick enough to stand a boil-out and the amount of metal etched away is minimal and safe. Is that true, or should I worry that the acid boil will burn the water jackets dangerously thin, with the possibility of developing a water leak into my exhaust?

Tom Neale: I've agonized over that issue many times on my boats. I've always replaced exhaust risers every five years or so, and also my exhaust manifolds, especially if they're raw water (saltwater) cooled. Your friends may be right, and I've known many people to get by with far more years than five by doing just what they recommend. But IF those walls fail, you may have lost your engine, or at least very seriously damaged it. When they fail, you have raw water running into your cylinders, filling cylinders with the pistons in the down position, and eventually getting into those with the pistons in the up position. It'll also end up in your oil pan. If you don't fire off the engine soon after it happens, the rust can ruin the engine. If you do try to fire off the engine, water standing on top of the pistons can cause a hydrostatic lock resulting in bad damage (such as a bent connecting rod). I'm not a great risk taker, and don't want to worry about it, or take the chance, considering the cost of replacing them and the cost of repairing the disaster if they fail.

Fuel For Thought

I was discussing the method I used to measure the fuel consumption on my 1988 Sea Ray. I wanted to get the best measurement without resorting to any special valving or metering of fuel. I topped off the tanks, idled to a waypoint outside the harbor, and ran a GPS course to another port for about two hours, at a constant RPM. Repeated this for the return course and topped off my tanks. I ignored any time at idle, only basing my calculation on the time at cruising speed. One of my friends felt that I should've included the idling time as well. I felt the time spent at idle would consume a very small amount of fuel but would be a significant influence on my calculation; although, I understand that it does introduce an error. I'd like to know if the method I used is better than including the idle time. The idle time was about half of the total time at speed.

John Adey: Fuel consumption is a hotly debated topic in both boating and, more traditionally, the automotive world. It really depends on what you need from your measurement. You have a test that told you what your consumption was at a certain RPM. In an industry-accepted test, we'd use eight points of measure from idle to full throttle and then plot the results on a graph. This gives data across all modes of operation. Then an average can be calculated. This is quite a long day of testing! Your style of boating may favor the time spent at plane vs. idle to get a more "personal" measurement. So, you have some data, it's up to you if you'd like more! To see how the industry does it, visit and search for a document called ICOMIA Standard 48-11 Measurement of boat fuel consumption, published in July of 2011; it's a free download and a very simple standard to follow.

Hold On

I'm looking for a new anchor. So far I only boat in pretty calm waters. But when trying to set my anchor on a local lake, I couldn't get it to set. Should I get an anchor heavier than what's recommended for my boat?

Tom Neale: Your difficulty in anchoring may have been because there are some bottoms where nothing will hold well. This includes hard (rocky), heavy grass, and extremely soft mud bottoms. Also, some bottoms have poor holding areas surrounded by good holding areas. As to size, bigger (within reason) is always better. Never assume you'll always anchor in calm waters. Of course, if your boat has long overhangs or a fine bow, too much weight in the bow can become a concern. We've lived on the hook over many years for several months at a time in many different areas. I personally prefer to have aboard the original, patented CQR, and a Fortress. The CQR has been tried and true for years all over the world. The Fortress has tremendous holding power and is very light.

We carry two types because of the variety of bottom types. The Fortress, for example, will set better in hard sand than the CQR. We also carry a "fisherman's anchor" which we sometimes use in rock and grass, although nothing's really good there. Use as much chain as you can afford (in weight) between your nylon-stranded rode and the anchor. This helps the anchor to set and hold and reduces the amount of chafing on your line. Anchoring tactics may help you, but there are too many to detail here. I covered some in my book "All in the Same Boat" published by McGraw Hill. You can probably find it in a library, or on  

— Published: April/May 2013

Cleaning And Polishing Fiberglass

1. The first step in restoring the gloss to dull gelcoat is always a thorough cleaning. Add a cup of detergent to a gallon of warm water, and use a sponge to wash the surface with this solution. For mildew stains, add a cup of household bleach to the mix (wear rubber gloves).

2. Next, before you polish or wax your boat, degrease it with MEK or acetone (keep the gloves on for this).

Photo of Tom Neale using a Shurhold Dual-Action Polisher

3. Remember, polish is an abrasive, not a coating, used to sand off a pitted surface. In some cases, the gelcoat may be weathered so badly that you need the stronger abrasives of a rubbing compound. Make sure to remove all wax first and don't rub too long in one place.

4. Once you're finished polishing, apply a coat of wax to protect the surface and improve the gloss. An electric buffer can take a lot of the work out of waxing and polishing, but don't substitute an electric drill with a buffing bonnet attached. You'll either ruin the surface or the tool.


Meet the Experts

Photo of Beth Leonard

Beth Leonard
BoatUS Magazine's technical editor, Beth Leonard, grew up powerboating, waterskiing, and fishing on Lake Ontario. Since 1992, she and her husband have completed two circumnavigations on two sailboats, doing all maintenance themselves. They also installed the systems on their 47-foot aluminum sloop. Beth has written The Voyager's Handbook, the how-to bible for offshore sailors, and hundreds of technical articles.

Photo of Tom Neale

Tom Neale
He's cruised long distance with his family for most of his adult life. He can take apart and fix almost every system aboard, has written two books, filmed a two-set DVD on East Coast cruising, written for top marine magazines, and has won nine first-place awards from Boating Writers International and many awards for his technical writing.

Photo of Don Casey

Don Casey
One of the most consulted experts on boat care and upgrades for 30 years. He and his wife cruise their 30-footer part of the year in the eastern Caribbean. His books include Don Casey's Complete Illustrated Sailboat Maintenance Manual, and the recently updated This Old Boat, the bible for do-it-yourself boaters.

Photo of John Adey

John Adey
The president of the American Boat & Yacht Council, John has been in the industry since 1990, with experience from a yacht brokerage and boatyard to owning a marine supply store. He and his family sail their classic 1976 Irwin ketch, a boat he completely restored.


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