Solutions from the BoatUS Tech Team

Barnacle Bills

Published: June/July 2014
Propeller illustration
Illustration: Bill Roche

How do you prevent barnacles from growing on the stainless shaft and bronze prop? I have a mooring in Brunswick, Maine. When the boat was pulled last fall, the shaft and prop were completely covered and had to be scraped off.


Tom Neale: For more than 40 years I've been looking for a paint or anything else that will stop barnacles from growing on my strut, shaft, and props. I haven't found anything that works to my satisfaction as much as a regular program of diving and scraping. There are some rather expensive products available, and I've used some, but I prefer the manual method. I even painted on STP Oil Treatment one spring years ago when many of the local Chesapeake Bay watermen were swearing by it. Examples of products that some have found helpful are Propspeed and zinc paint such as Pettit's Barnacle Barrier, or generic "cold galvanizing" sprays. Copper-based paint on running gear can result in electrical interaction, doesn't stay on well, and can impair the gear.

Tip iconFor more on bottom paint, read "The Lowdown On Bottom Paint" in the April 2014 issue.

Part of the problem is the constant abrasion you get on the prop from particulates in the water when the boat is running. Some people cover their prop(s) when they're not running the boat with a plastic garbage bag with a trip string so that they can easily pull it off before getting underway. But this is a hassle, probably involves diving at least to do the install, and you wouldn't want the bag to come loose and float away.

If your boat is in current with a lot of nutrients flowing by, this will greatly accelerate the growth. And warmer water also usually results in more rapid growth. I dive, either free diving or with a Brownie's Third Lung. If you keep up with it, the job isn't bad, but you must know what you're doing in and under the water and be in good health. If you don't want to dive, there are usually commercial divers around and the cost of hiring them may well be worth it when you consider the extra cost of fuel when your props, strut, and shaft are fouled.

If someone has a tried-and-true solution, meaning at least a full season with a lot of running and little or no fouling, and repeated success over more than one season, please email us and share the good news.

Which Way To Wrench?

I need to tighten the packing around the propeller shaft. It has a locking nut, and a nut to compress the packing. Looking toward the stern from the engine, does the lock nut turn clockwise or counter clockwise? Does it depend on the shaft rotation? My prop walk is to starboard.


Don Casey: The rotation of the shaft has no impact. Looking toward the stern from the engine, the lock nut is going to turn clockwise to loosen it. Conversely, the packing nut is going to tighten when turned clockwise, because clockwise moves both nuts toward the stern. Be sure to use two wrenches, one holding the packing nut when you release (or tighten) the lock nut. You might also need a pipe wrench to hold the box at the flange that sits on the stern hose to keep the box from spinning inside the hose if the packing nut is stiff. Except for access, this is usually a pretty easy job that goes off without a hitch.

Replace Or Not To Replace, That Is The Question

I read "Avoid Getting Hosed" in your February 2014 issue. I installed a new engine in my boat 11 years ago with SAE J1527 alcohol-resistant hoses. The local dealer says I should replace them after 10 years if I use ethanol fuel, which I do. Is it really time?


John Adey: If I owned a boatyard and was doing the service, without question I'd recommend replacement of 10-year-old hose. ABYC Standards (H-24 Gasoline Fuel Systems) recommend an annual fuel-system inspection, which I would perform. There's no magic destruct date on fuel hose. Remove one, and swab the inside with a Q-Tip. If black stuff comes off, the hose is deteriorating. Also check the outside for cracks or stiffness, both signs of deterioration. If all looks good, specifically around the hose barb where the hose is flexed and clamped, then you're probably OK for another year until your next inspection.

What's It Worth?

Is there a Kelly Blue Book or similar publication on boat prices like there is for cars?


Beth Leonard: There are several value references published for used boats, but it takes experience to know which, if any, to use for which boat types, and how to interpret the data. Such guides typically use data at least 18 months old by the publication date to which they apply some sort of algorithm, hoping to approximate current market values. Some are more successful than others.

One is completely free, Another is available for limited use free after registration, The others require subscription or purchase — not inexpensive, either way. BoatUS offers free, used-boat Value Checks to members, based primarily on the purchase histories of similar vessels as recorded in our marine-insurance department database, the detailed knowledge of our Value Check professionals, and other industry sources. Our estimates represent typical values for that manufacturer, model, and year, equipped to normal standards for the intended use. They're not vesselspecific appraisals, which can't be done sight unseen. But they'll provide objective guidance as to what a boat of a specific model and age is worth on the open market. Go to for your free estimate.

Two Cents ' Worth

I have a 42-foot Carver with the usual 340-hp Mercruisers. These are topped with Quadrajet carburetors and have logged about 1,000 hours. I'm planning on rebuilding or replacing the carbs in the interest of efficiency. Any advice?


Don Casey: I haven't had much to do with four-barrel carbs since my wasted youth trying to wring extra horsepower from big-block Chevys. That said, if you're easy on the throttles, I'd expect the Quadrajet to be as economical as any other carb, maybe better because the front barrels are smaller. A rebuild is also the cheapest and easiest option.

If you get info from a reliable source that you can make significant economy improvement with a different carb setup, my guess is that will be for Edelbrocks. There's a pretty standard relationship between energy in the fuel and engine output. When you're running these big engines at speed, they're going to burn a fixed amount of fuel no matter what carb is fitted, assuming the carbs are in good shape and tune. Run the numbers on potential economy improvement to see how many hours you'll have to operate to recover the cost of the different carbs. Without compelling evidence of really significant improvement, I'd stick with the Q-jets.

1 | 2 | Next

Get In Touch With Our Experts

Contact these experts at the BoatUS Ask The Experts site at where you'll also find hundreds of questions and expert answers already archived, with new questions and answers uploaded regularly by our Get In Touch With Our Experts team. Online, you'll also find 11 other experts in different fields, ready to help. From your questions, we'll select a few of the most generally interesting for use in future magazine columns. The best part? This service is free to members.


 Recommended Articles
Gray rule

Thumbnail photo of propeller damaged by rockFixing Boat Propeller Problems

How to diagnose and remedy common problems

Thumbnail photo of a bilge hoseDon't Get Hosed By Busted Hoses

Not replacing a worn-out hoses, or using the wrong one, can lead to problems ranging from a smelly head to a sunken boat

Thumbnail photo of solar panels on boat cockpit roofSolar Panels

What is a solar panel and how does it work?



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.


BoatUS Magazine Is A Benefit Of BoatUS Membership

Membership Also Provides:

  • Subscription to the print version of BoatUS Magazine
  • 4% back on purchases from West Marine stores or online at
  • Discounts on fuel, transient slips, repairs and more at over 1,000 businesses
  • Deals on cruises, charters, car rentals, hotel stays and much more ...
  • All For Only $24 A Year!

Join Today!