Ask The Experts

Solutions from the BoatUS Tech Team

Wrong-Way Flush

There's backflow into my head when underway and also when docked if the holding tank is 3/4 full. Should there be a backflow preventer in the system?

Tom Neale: It's important to know whether the waste and water are coming from the top (clean water inlet) of your head, or the bottom (waste discharge). That will tell you which plumbing runs are involved. I assume the holding tank backup is coming from the bottom. The backflow from your holding tank may be because it's installed too high in relation to the toilet. It could also be related to expansion from accumulation of gas in the tank. Check to be sure the tank vent is clear. Backflow while underway may be caused by a thru-hull positioned so that water pushes into the hole when the boat is in motion.

Normally you wouldn't want to put a "backflow preventer" such as a foot valve or flap valve in your head plumbing. They result in clogs and seldom last long in that environment. However, it sounds like you need a vented loop with an anti-siphon valve at the top of the loop. It should be of sufficient height to stop the problem. This should be in whichever line(s) is involved. If you're installing a vented loop in the intake line, be sure to follow the instructions of the manufacturer. If it isn't put in the right place, it could interfere with the pump's suction of incoming water. If water still comes in while underway, you may need to reposition the thru-hull when hauled, or put a clamshell strainer with the high part forward (I'm assuming you're dealing with the intake line) or some other reverse-scoop arrangement so that forward motion of the boat no longer forces water in.

Many heads rely on a "joker" or "duck" valve at the head discharge to prevent backflow. This valve is entirely inadequate to prevent flooding from the sea, but should prevent backup within the system. Often this becomes torn or worn from use, brittle from deposits, or even inverted from pressure downstream, causing smelly backflow. The solution is to replace the valve.

Paint Revival

A buddy told me that after leaving my boat out of the water all winter, I should "reactivate" the bottom paint by using a scrubby, or light sandpaper, to expose its antifouling capabilities again. Does bottom paint go dormant when it's out of the water too long?

Beth Leonard: The answer depends on whether your bottom paint is ablative (soft) or hard. The copper in a copolymer ablative paint is not exposed to air but is locked into the paint. So on most ablative paints, a light scrub with a no-scratch, plastic household scrubber will remove any dirt or contaminants and you're good to go. That said, a few ablative paints used on racing boats are so soft that even a light scrubbing may remove most of the paint. If you think your paint might fall into this category, check with the paint manufacturer first. A hard modified epoxy paint has an open binder, so the copper is exposed to air and it will oxidize over the winter. Don Zabransky from Pettit Paint says, "It's very difficult to say how long a boat can sit without this kind of paint becoming ineffective." He recommends sanding a hard paint down and applying one fresh coat before launching to ensure protection for the season.

Bottom Blisters

I just read Don Casey's article on hull blisters (June 2013) and found it both informative and a little disconcerting once I realized blisters are present on my 2000 Regal 2100 LSR. I'd noticed them before and honestly never given them a second thought, thinking they were harmless or even purposely there from the factory — like dimpling on a golf ball. The blisters are very small, with the largest of them being smaller than a dime. They're very prevalent just below the waterline around midships, and also show up on the rear third of the hull. A few have cracked and peeled off, leaving a very shallow pockmark in the gelcoat. My boat was kept in a slip for its first decade but is now trailered. If I don't address the blisters now and continue to trailer the boat, am I risking exponentially raising the eventual repair cost? If the blisters do not increase in size or number, do they need to be addressed at all?

Don Casey: Answering the last question first, you really should repair at least the open blisters just to shield the exposed laminate and to make the bottom of the boat smooth again. Even small pockmarks will affect performance. The repair is really nothing more than cleaning out the blisters and roughing their inner surface with sandpaper, then filling them fair with epoxy putty. As to whether failure to make any repair presents a risk either to the boat or eventually to your pocketbook, the answer is probably no. With the boat no longer in the water except during use, the likelihood of the laminate absorbing water is negligible, meaning new blisters are unlikely. The existing ones may continue to crack open and the cap peel away, leaving additional depressions in the hull surface.


How should I take apart the engine exhaust hose on our 400 Sea Ray Sedan Bridge? There are clamps on either end of an insert. Does it slide either way to enable it to come apart?

John Adey: I'm not familiar with your specific model, but it sounds like you have two flexible hoses joined by a fiberglass or metal section. This should (with some effort depending on age) slide to either side to allow removal. Check around first; it may be easier to remove an upstream or downstream connection first. Replace BOTH CLAMPS when you reinstall; this is an ABYC requirement and an important carbon-monoxide protection that prevents exhaust from leaking into your cabin. Likewise, if you damage the hose during removal, replace it if you can't achieve a proper seal.

How Long Is Too Long?

I have my boat in storage and it will remain there for the next two years. The outboard was winterized three years ago. How long can it stay without further service? What service should it have?

Tom Neale: It isn't clear from your question how long and under what circumstances your boat has been laid up, but it sounds like you stored it three years ago. How much longer you can go depends on the type and quality of service already performed and how it's stored. For example, your outboard should have been flushed with fresh water and the cylinders should have been "fogged" according to manufacturer's recommendations. Also the carburetor and/or jets should have been flushed with a product to prevent gas from turning to a varnish-like substance and then run dry to remove any gas. The gas in the tank will have expired, even if you added good additives. So you're probably going to need to have the tank drained by a qualified professional.

If it were my motor, I'd have a qualified mechanic check it all out now and do the things the manufacturer recommends for storage. Even if it was done well the first time, after three years, it's a good idea to do it again. Some things aren't going to fare well, regardless. For example, the impeller blades in the water pump have been cramped in one position all this time, and before you start using the motor again, you should replace the impeller.

If the boat is stored inside a climate-controlled area, you should be in much better shape than if it's stored outside and/or under a tarp. Mold, mildew, and rot can cause serious problems when a boat is just sitting. The boat should be well-ventilated to help lessen this. Other problems, such as freezing of your control cables inside their sleeves (if that's what you have), can be minimized by working the controls periodically. Boats need to be run, and if you're letting it sit for this long, you or a good mechanic should periodically visit it, inspect and work components (if it's safe to do so), and make sure all is well.

High And Wet

We had to leave our home in Oriental, North Carolina, midsummer for about a month in July of 2011, so I put my 25-foot Carolina Classic on the trailer and parked it in the yard. I picked a high spot - about four feet above MHW [mean high water] — away from overhanging trees and set it up, bow high, with the drain plug out. Along came Hurricane Irene. I got back a few days after the storm to find that the boat and trailer had floated, even with the plug out, and bounced about 10 feet from its original location. I probably should have set some ground anchors to keep it from floating away. I'm still not entirely sure about the right approach to the drain plug. Yes, leaving it out lets water out, but in the event of high water, it also lets water in. Please poll the experts and offer an opinion.

Beth Leonard: In the wake of Sandy, we debriefed the BoatUS Catastrophe (CAT) Team, and talked to many marinas about what worked and what didn't. First, given that the boat is trailerable, the ideal thing would be to find somewhere to leave it where surge wouldn't be an issue. That would be by far the best solution and most likely to keep your boat safe.

If you can't do that, then, yes, ground anchors would be a good idea. Depending upon how much surge you could be subject to (Irene probably gave you a good idea), you might not want to strap the boat down tight. We saw marinas successfully "leash" boats in Sandy, allowing them to float up with the surge but remain roughly in place and settle back down when the surge subsided. Make sure to lash the boat firmly to the trailer so it doesn't come down on the trailer in a different orientation or wander off on its own.

The drain plug is the most complicated part, especially in your situation where you're leaving the boat for long periods. Those marinas that left drain plugs in during Sandy suffered much less damage to engines than those that did not (most boats with their drain plugs out flooded and sank on land). Yet we still advise leaving the drain plug out for the winter to protect against freeze damage. Ideally, you'd have someone who could go put the drain plug in before a named storm. Alternatively, purchase a one-way drain plug (such as the CR Marine Automatic Drain Plug), leave that in, and cover the boat. That way, water would only get into it if the cover were ripped off, and then the drain plug would work to drain the boat while protecting it from surge. These plugs are not foolproof because they can be more easily blocked by debris than the drain hole, or can get stuck in the open position when a leaf or twig gets into them, but they would offer some protection in the event of a big storm.

Weeping Pump

I have a 1998 Mercruiser engine with about 1,000 hours on it. The seawater pump is starting to show grease coming out of what looks like a vent hole. Does this indicate the bearings have overheated and the pump should be replaced? I change the impeller once a year but haven't done anything else to the pump.

Don Casey: When the raw-water pump begins to weep grease, this tells you that the lip seals in the pump are failing, meaning not only is the grease leaking away from the bearings, but raw water is almost certainly leaking into them. It is only a matter of time — typically a pretty short time — before the bearings fail. Replace or service the pump without delay.

Spark Hunt

How do I check a coil on a 1999 90-hp Yamaha?

John Adey: The simplest way is with a commercially available spark tester that contains a clear section so you can see the spark jump from one contact to another. You can rent one at an auto-parts store or purchase one for your toolbox. Coils are very high-current devices, so attempting to hold the plug and wire while grounding it to the block may cause a massive shock. Alternately, call your local auto store or repair place and see if they have a coil tester that will work for your coil. In this case, you would remove the coil and bring it down to the location so they can run a test on it.

Hold 'Er Off

I keep my 25-foot sailboat on a creek off the Chesapeake Bay. I need to keep the boat on the side of a pier, perpendicular to and stern to the pier. We drove two, eight-foot galvanized pipes down about four feet into the mud and sand bottom at the bow. The creek is relatively well protected, but with a good north wind, the waves can build up. I'm worried the pipes won't hold and my stern will hit the pier. I might sink a mushroom anchor with a chain rode about 15 feet off the bow. I've never used a mushroom anchor and was wondering what size to buy.

Tom Neale: I'd put out an anchor, but wouldn't use a mushroom. These are difficult to really get set in, especially with sand typical to the Chesapeake, and you're often never really sure it's set well until a lot of weather goes by. I'd use a Fortress, going with their recommendation as to the size for your boat, plus one size for good measure. I'd use all chain, the bigger the better, except for the last few feet to provide some elasticity, and, of course, to make it easier to secure to the boat. Set the anchor with as much force as you can from the direction of the wind that concerns you. I've found that these anchors really dig in, although a really bad storm can outdo us all.

Watering Batteries

I know keeping my batteries topped off is important, but I can't get my plastic pitcher with the spring-loaded spout in the space to fill them. They're under the fish box with about four inches of clearance. I have to disconnect the cables, then, lying on my belly, wrestle the batteries out on the cockpit deck, check the water levels, then put them back. Is there an attachment I can get to stop the water running over when it reaches the appropriate level?

Don Casey: Not that I'm familiar with. In your circumstance, I'd use a mirror, a bright light, and a squeeze bottle fitted with a length of tubing. With the light and mirror you should be able to assess the water level, and with the squeeze bottle and tube you should be able to add water in situ. When it's time to replace the batteries, consider a sealed type such as an AGM. Make sure the batteries you select can accommodate the voltage of your existing charging system. 

— Published: October/November 2013

The Scoop On Scope

Scope is often defined as the ratio of the length of deployed anchor rode to the depth of the water. Wrong! Scope calculations must be based on the vertical distance not from the sea bottom to the surface of the water, but from the sea bottom to the bow chock or roller where the anchor rode comes aboard. For example, if you let out 30 feet of anchor rode in six feet of water, you may think you have a 5:1 scope, but if your bow roller is four feet above the waterline, your scope is actually 3:1.

Scope is required to keep the pull on the anchor horizontal. The more upward pull on the anchor, the more likely it is to break free. Minimum scope for secure anchoring is 5:1. Seven-to-one is better where you have the room. A length of chain between the line and the anchor (at least 20 feet) also helps to keep the pull horizontal.


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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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