Ask The Experts

Solutions from the BoatUS Tech Team

Disappearing Zinc?

I just read an article in the Caribbean Compass; they're advocating aluminum anodes as opposed to traditional zinc. What are your thoughts?

Don Casey: I suspect aluminum-alloy anodes are in all our futures because of the environmental implications of cadmium in zinc. I've seen no report of switching to aluminum resulting in damage to the underwater metals on a protected boat, but the cost of aluminum anodes has been higher. Aluminum also works well in brackish water. If you make the switch, all of your anodes must be aluminum. That's a problem in many locales as local marine suppliers often don't stock a wide selection of aluminum anodes. That will eventually change.


I have a 2000, 50-hp. Mercury Bigfoot, 4-stroke outboard. The engine starts right up. However, after idling at the dock for a few minutes, the engine revs to 3,000 rpm and stays there all by itself! The throttle linkage doesn't move when this happens. It's like the motor is haunted.

John Adey: I have a feeling there may be a problem in the electronic control module (ECM). The only way to diagnose the issue is to have an authorized Mercury dealer plug into the ECM with a laptop with the Mercury service software, and watch what the engine is doing when it revs up. An improper interpretation of the temperature sensor or any number of things could cause the ECM to increase the RPM. Superstitions aside, I think your dealer can make the ghosts go away!

Plugging The Holes

I installed a new fishfinder. The new transom bracket was different than the old one so I had to plug the old screw holes. I used Marine Tex and inserted it with a plastic needle as far as I could, and let it dry for two days. Is this a good way to seal a hole below the water line?

Tom Neale: Marine Tex is good stuff, but in my opinion it's a bit brittle for that job without doing more. To be sure of a waterproof repair, I'd apply several layers of fiberglass and epoxy resin over the two holes to be sure that voids don't develop. This could allow water to seep inside the transom coring potentially causing serious long-term damage. At this point I'd leave the filler there, but I'd thoroughly sand the area surface, making a slight dimple to avoid a raised area. I'd clean with a good solvent, then apply the resin and glass according to the product instructions. I use West System materials. I'd flare the edges of the repair smooth after it dried. You may end up with a slight raised area over the old holes, but you could be far more certain that the filler seal wouldn't be compromised from pressure or flex. This entire job wouldn't take long nor would it cost much.

Reverse Course

I have a 1979, 25-foot Chris-Craft. The original engine was counter-clockwise rotating, making the wheel rotation clockwise. The rudder is off-center to port. The new engine is standard rotation, making the prop rotation now CCW. Can I move the rudder? The reason for the move is that I have no control of boat in reverse. It only goes to starboard.

Don Casey: Moving the rudder is unlikely to make any difference in backing. The problem is that the rudder is leading the prop when going backwards so the prop wash is toward the bow, not over the rudder. As a result the rudder has no effect at all until the boat is in motion. Even then, the small rudder is going to exert small turning force, often not enough to counteract the "walking" effect of the prop. Unless you have personal experience to the contrary, I think the only difference reversing the change in rotation will cause is in the direction of the walk. A right-hand prop (CW) walks to port when going astern. A left-hand prop (CCW) walks to starboard. Lots of boats with single screws cannot be made to back straight, not just your old Chris.

The reason for the offset rudder has little to do with handling. Chris-Craft has long offset rudders on some of their boats to allow the prop shaft to be removed without the necessity of first removing the rudder. That said, the choice of offset side might have been influenced by the designed direction of prop rotation, but any difference in handling characteristics of shifting the rudder to the opposite side a couple of inches is unlikely to have enough effect to justify the effort of making that change.

Gain A Plane

I have a 1983 Chris-Craft Catalina without trim tabs. This boat is very hard to plane. Is there an area in the boat where the heavy items should be stored? Am I hurting the planing process with heavy tools, extra anchor, and fluids up front?

Tom Neale: Many boaters experience this problem. Usually, the best way to resolve a planing problem is to communicate with the builder. If you think the issue is weight, carefully experiment with moving heavy items. Too much weight up front will hurt planning. It's usually better to store heavy items in the wider midships or after sections, low down. If you store weight in areas that don't fall within the weight-carrying design/build parameters of the boat, you could impair its stability as well as its planning capability. This could be a serious safety issue, and is an important reason to consult with the manufacturer. Adding trim tabs may help, but it should be done by a well qualified yard.

Photo of a prop on a boatThe proper prop can make all the difference.

There are other things that could affect trim. The engines may not be performing properly. The props may need work (re-pitching, cupping, or balancing, etc.). Sometimes changing props solves this problem, but finding the right prop is part science and part magic and requires experts. The boat may be underpowered. There's even the unlikely possibly that the hull has absorbed water over the years and gained weight. A good surveyor with a moisture meter could help you determine this, although I'd investigate other possibilities first. The best news is that you may simply have a dirty bottom or running gear. Often it's helpful to visit owners' forums on web sites such as the BoatUS web site, clicking on "Boater to Boater" on the left side and then, "Boating Groups."

Rattle & Hum

I own a Sea Arc [aluminum] welded jon boat with a 2010 90-hp. outboard engine. What can I install between the engine-mounting bracket and transom to eliminate vibration? There appears to be nothing wrong with propeller or engine.

John Adey: There are several aftermarket solutions to "soften" your problem. Before doing anything drastic, make sure that all the holes in the transom and outboard bracket are of the proper size (e.g. no room for movement) and the bolts are to manufacturer's specs. If you've done this, then try some type of rubber/nylon interface between the O/B and the transom. Nylon and rubber bushings are easy to come by and install, but may not be resistant to oils, fuels, and other common marine liquids. If you choose to use an isolation method, be sure the materials can handle the normal use of the boat. Keep in mind there's nothing that can totally isolate the vibration of an engine installed on an aluminum boat, but it should not be uncomfortable and loud.

Pump Now Or Later?

Our nine-gallon holding tank is not full after two weeks use. Should we pump out when it's partially full or wait until it's full? We're using the chemicals recommended by Raritan.

Tom Neale: I'd pump out my holding tank whenever I got the chance. Holding the stuff in the tank can be dangerous because, as it decomposes, it could form potentially explosive hydrogen-sulfide gas. There's also the smell and the possibility for trouble should your tank or its plumbing develop a leak. Also, you never know when the pumpout station you plan to use is inoperative or inaccessible for some reason, in which case you'd have nowhere near to pump when your tank fills.

Pain In The Gas?

I'm in the market for a 23- to 26-foot walkaround. Having had fuel-tank issues with past boats, accessibility is a major concern. Are there boats in this range built with fuel tanks that can be removed without cutting the deck? Frankly I'm surprised it's not a Coast Guard requirement for all boats.

John Adey: This has always been a point of contention between boatbuilders and owners. After some research, it appears that the best you'll find on most of today's boats is a "cut mark" molded into the floor. This indicates the area where the tank is located should it have to be replaced. Your concern about this not being a USCG requirement is certainly well founded; that said, there are extensive regulations and standards on the tank itself. The tank model chosen by builders has been tested to the point of destruction before a tank manufacturer can sell it. There are shock tests, pressure/vacuum tests, and even exposure to 2 1/2 minutes of free burning flame. If installed properly the tank should outlast the boat. Each fitting is required to be accessible for inspection, which ABYC and the USCG recommend is done annually.

Though you may still have doubts, the goal of the USCG and ABYC is to ensure that the tank never has to be removed. The best thing to look for is a boat certified by the National Marine Manufacturers Association. Boat companies subject themselves to an annual inspection that confirms that they're complying to the applicable standards for each model they build. For more info on fuel-tank requirements, refer to the following: USCG. A list of NMMA-certified manufacturers.

Outing Interruptus

I have a 1987 Sea Ray Weekender that's developed a tendency to stall when I engage forward or reverse. More aggressive shifting has helped, but when we tried to take one last scenic fall ride, we couldn't get off the dock. The motor continued to stall after eight to 10 attempts. I've been told there's a switch that controls this?

Don Casey: There's a little switch that's probably the source of your problem. It's called a shift interrupter, and it momentarily interrupts the ignition when shifting to take the load off the gears. More often than not, however, the problem is not the switch. Instead it results from stiffness of the drive shift cable or shaft. The switch is activated by tension on the cable and when the cable requires extra force, it causes the interrupter to be in play longer than designed, resulting in stalling. Try disconnecting the shift cable from the transmission and shifting from into forward or reverse. If you have difficultly, the cable needs replacement. You can try lubricating both ends of the shift cable, but for a permanent fix you're probably going to need to replace the cable. 

— Published: April/May 2012

Meet the Experts

Photo of Don Casey

Don Casey
He's been one of the most consulted experts on boat care and upgrades for 30 years, and a panelist on our "Ask The Experts" website for a decade. He and his wife cruise aboard 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 VP/Technical Director for the American Boat & Yacht Council (ABYC ), John grew up boating. He's 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. John is a trusted source for technical information for industry professionals.

Photo of Tom Neale

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

Photo of Bob Adriance

Bob Adriance
The editor of Seaworthy, the damage avoidance newsletter of BoatUS Marine Insurance, Bob has written hundreds of articles on safety, loss prevention and causes of boating accidents. His 2006 book, Seaworthy, Essential Lessons of Things Gone Wrong, is based on 20 years of real claims files. He's owned Folkboats to J-Boats and currently sails a 36-foot sloop.


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