asktheexperts
By Our Technical Editors


Where Does The Gunk Come From?

In our ongoing new column, devoted to the technical challenges that frustrate all boat owners, our top tech team is standing by with the answers.

In my sailing catamaran, the brass pickup tube inside the plastic fuel tank is severely fouled with a black substance. Once dry, it can be scraped off with a fingernail and crumbles to dust when rubbed between fingers. Fouling is both inside and outside the tube, but much worse on the outside. The tank interior is clean on the sides and bottom and doesn't have any deposits. I use diesel fuel with ValvTect Diesel Guard and ValvTect BioGuard biocide. Regular fuel filter changes don't evidence any fouling. Do you have any idea what the fouling on the fuel pickups might be?

Don Casey: It's probably some form of microbiological growth that somehow finds that the brass provides a viable environment for growth despite your chemical treatment. You can determine if it's biological by spraying a scraping of the deposit with chlorine bleach. If the substance turns white, it is biological. It might also be asphaltene or some other tar- or varnish-like residue from the fuel itself. Here the usual test is to put a scraping on a piece of glass and spray it with WD-40. If the contamination is oil based, bleach will have no effect but the WD-40 will emulsify it.

A third possibility is corrosion forming on the dry part of the tube as the tank level declines. When it's dry, the corrosion formed on brass should be a light green color. Examine the "powder" carefully to see if it looks like corrosion. In all cases, if your tanks are otherwise clean, simply clean the pick-up tubes — inside and out — and refit them, making a note to check on this again in a few months. It might have been the one-time result of some earlier condition with the tank or fuel.

Freewheeling Prop A Good Idea?

This past September, my wife and I purchased a Carver 405 aft cabin. Does it do any damage to a motor or transmission to cruise at 8-10 knots using only one motor? Some people say yes, some say no, some say put the motor not being used into gear to keep the shaft from spinning. I always start both motors and use them for docking, so fluid is pumped through both transmissions.

Don Casey: The correct answer depends on the type and construction of the transmission and should be directed to the transmission manufacturer. That said, almost any transmission can safely freewheel for a couple of hours without significant consequences. I'm guessing your transmissions are ZF Hurth, and if so, these boxes can safely freewheel. There will be, of course, bearing wear, both in the transmission and for the shaft, but it will be negligible. You will need to know what kind of shaft seal you have because a dripless seal lubricated with water from the engine will burn up if the shaft spins without the engine running.

It may seem counterintuitive, but the drag of a freewheeling prop is significantly more than that of one locked in position because the spinning blade develops lift — exactly like an autogyro. For this reason, you might want to lock the prop rather than allow it to freewheel. In almost all transmissions, that means putting the transmission in reverse, never forward. In forward gear, the water flow over the prop causes the shaft to exert rotational forces on the forward clutch, with clutch wear almost a certainty.

Water In The Box

I found water in the electronic box containing our Simrad electronic compass. We don't know how water got in there. Should we relocate the new replacement, or is there a way to seal it better than the original, so water won't enter the compass again?

John Adey: You must determine how the water got onto the unit inside the boat. If you have a leak that's damaging the compass, then it's quite possible it's doing other damage as well. Wooden bulkheads and deck core can all be damaged over time if you cannot get to the leak. Perhaps water is wicking down the cable from a location that's not immediately in the area of the unit.

Sometimes these parts can be effectively dried if they haven't been energized while wet. CRC's QD Electronic cleaner, followed by sealing the unit in a bag of rice for a week or so, works quite nicely. Word of caution, however: Put some hours on the item before relying on it to make sure it can go the distance.

When reinstalling (the new one or the old one), consider adding a drip shield to the top of the compass housing. A piece of plastic milk bottle is about as low-tech as you can get. Installed properly, this will direct any water away from the unit. I recommend against additional sealing of the box; this will prevent any humidity from escaping and causing additional damage. I am sure Simrad has a method to their enclosures that prevents moisture buildup. Location is a different story. If you were satisfied with the operation of the compass as it was, I would keep it there. To relocate, I suggest getting the installation manual from Simrad (www.simrad-yachting.com) and following their instructions. First things first — find that leak!

Shift To Stop

I have a 150 Mercury outboard that stalls when the throttle is moved from the slow-idle position to the shift-neutral position. The engine stops as if the ignition has been turned off. Is there an electrical stop switch in the control that could be causing this shutdown?

Tom Neale: Many of these shifting control mechanisms have an electrical safety switch within the unit. The purpose is usually to keep you from starting the motor in gear. The switch itself may be defective or there may be loose or deformed parts inside, interfering with the switch. I've disassembled some outboard-shifting control mechanisms and some are very complex inside, with much to go wrong, in my opinion. If there is no electric wiring running from your shift mechanism, then the kill switch is probably elsewhere. Sometimes the kill switch is located on the engine. If your system is rigged this way, the same issues may be at that location.

I'd suggest that you get someone to find out what's going on before trying to use the boat again. It may be that you just need to remove the shift mechanism from the console or look up from underneath (depends on how and where it's mounted) and the problem will be obvious. It could be something as simple as wiring. But any of this could involve a potentially serious safety issue.

Jumpy Tach

I have the 2002 Yamaha 250 Saltwater Series on my 23-foot Sea Pro Walkaround. The tachometer intermittently reads 1,000- 1,500 rpm higher than actual. I've been told possibly a poor ground, but I have no idea where to check. Any ideas?

John Adey: To troubleshoot any dash gauge, I always start at the back of the instruments. The wires are generally crimped in ring terminals and bolted on studs. These are prone to coming loose and giving a bad signal, either ground (black) or tachometer sender (generally dark-gray). To add insult to injury, sometimes the negatives are "daisy chained" from stud to stud; one bad connection may affect the rest. Check the backs of the gauges, and then check the gauge itself. Flick it while running to see if it jumps to the proper reading; if so, replace it with the appropriate tachometer.

Next I'd check the engine harness connection at the outboard. Sometimes water gets in these connections and corrosion results. Disconnect the battery then pull the harness plug, inspect, clean if necessary, and apply "dielectric grease" available at a good marine-supply place or an auto-parts store. This grease is conductive and will maintain a good connection.

Floodgate Dilemma

Do you recommend that seacocks be in the open or closed position for equipment (generator, air conditioner) that is not being used?

Tom Neale: Normally, the safest thing to do is to close all seacocks that aren't going to be used when you leave the boat for a time — for example, between weekends. Of course, you wouldn't want to close a seacock if it's used by the bilge pump or drains your cockpit.

In theory, it's safer to close a seacock for equipment not being used when you're on the boat, but this means that when you turn on that generator or air conditioner, you must remember to open the seacock. Failure to remember could cause some very expensive damage to the equipment and even to your boat. And few of us have memories that good. (I don't.) So most people don't close seacocks for equipment they're not using while they're on the boat. That's why you should have good loud bilge alarms. The alarm should give both visible and audible warnings, hopefully loud enough to be heard by a passerby on the dock as well as by you with the engine running. If a leak from a hose or fitting or the seacock itself is getting water into your boat, the alarm should let you know because you're there.

If you do close seacocks when you're away from the boat, it's important to place a sign or warning to that effect at the ignition for the engine and generator (and any other device that may be damaged if it's run without the seacock being opened). Marinas may need to move your boat in certain circumstances, and the operator will need to know about that closed seacock. The same is true, for example, of an air-conditioning technician whom you may ask to do work.

Double Talk

My wife and I cruise the East Coast (Charleston, south to the Florida Keys and the Abacos, and north to the Chesapeake). We've been doing this since 1991 on our Catalina 30 via the ICW and offshore. The VHF radio installed on our boat is the original and I'm debating whether to replace it with a newer radio but wonder whether it's worth the effort. Everything works fine, but I've noticed my VHF doesn't seem to transmit as far or receive transmissions from as far away as the radios on some of my friends' boats. Most of these boats have fairly new radios and higher masts. Therefore, I wonder if my "problem" is the old radio or the difference in mast height, or maybe the antenna or even the cabling running from the top of the mast to the radio in the cabin.

I know there are other advantages a new radio could offer, such as MMSI capability, remote microphone and controls, etc. Do you think a new radio would improve transmission/reception range? Or is the more likely solution to replace the antenna on the mast with a new one? How likely is it that I'd also have to replace the cable running from the mast top to the radio in order to address this problem?

Tom Neale: We have two "ship's radios" on our boat as well as two hand-helds. We stand by on 13 and 16 because 13 is used for bridge-to-bridge communications between most commercial boats. Therefore we're more likely to be alerted if something is going on ahead such as dredging or tugs and tows or large-ship maneuvering. A hand-held is limited in range because its antenna is so low and because of its power output. I prefer to not have to use a scan function for standing by on 16 and 13 simultaneously because often a scan will clip out part of a transmission. And I like some of the features of the newer sets. Both of ours have a remote mike and this often comes in very handy. If I were you, I'd spend the money and get a new radio (and antenna and wiring for it) and use the older one as that all-important backup. The VHF is a critical safety tool, especially for boaters who do a lot of traveling.

Having said that, your present issue may indeed be caused by problems with your older VHF, but it could also be caused by your antenna, the cable or, quite likely, by the connections in the cable running from the antenna down to your set. That connection on top of the mast takes a lot of abuse. Sometimes just unscrewing the connections and spraying them with something like Boeshield T-9 or CRC 6-56 or similar product will make quite a difference and you won't need to replace the cable.


Plastic Surgery

I want to repair existing carpet snap holes in the non-skid of my Sea Ray Sundancer. I have to move all of them as the replacement carpet is about 1/2-inch off. What's the best way to plug those holes?

Don Casey: Epoxy putty is the best choice for filling screw holes in fiberglass. You can mix your own, but for your use, a pre-mixed epoxy paste such as white Marine-Tex will be easier and result in a less visible repair. If your non-skid is not white, you can tint the paste with a coloring agent.

The process is easy. Use a countersink bit to chamfer the top of each hole. This cleans up the contact area and makes the repair stronger by giving the epoxy a larger and more horizontal surface to adhere to. Without access to the bottom of the hole to seal it with tape, you may want to fill the holes in two steps. First put just enough epoxy putty into the hole to seal the bottom. Where holes are large, the putty can tend to drain through. In this case, use a bit of dowel to create a plug, or stiffen the paste with sawdust, talc, silica, or even a bit of wadded tissue. You're just trying to close the bottom of the hole.

When your plug has set, or if you don't need a plug, fill the hole completely with your epoxy putty, making it level at the top with the surrounding surface. Epoxy does not shrink during cure. As this is a textured surface, you can match the texture by stippling the putty with a finger, a cloth, or some other tool that gives you the desired effect. When the epoxy has cured fully, you'll have a permanent repair.

E10 Again

Various articles I have read in BoatUS Magazine regarding ethanol state that there's nothing that can stop phase separation. Various additives say they will eliminate this problem. What do you say?

John Adey: I contacted various engine manufacturers to find out what they recommended. In a nutshell, there's no "silver bullet" for phase separation. Several came back with some benefits of the ethanol additive itself, stating that it holds up to 5,000 parts per million of water (ppm) where traditional non-ethanol gasoline holds 120-150 ppm of water. That means that E10 is better at dealing with small amounts of water, but if separation does occur, you not only have alcohol and water at the bottom of the tank, you're also left with very low octane for the fuel above.

Some engine manufacturers warn against overuse of oxygen-containing additives (like alcohol or ether) contributing to high exhaust temperatures and lean running, which is not desired performance. The best solution is to ensure the problem doesn't get too out of hand to start with. Some hints:

1. Fill or empty the tank before each storage season to minimize the buildup of condensation in the tank due to the normal daily heating and cooling cycles. A completely empty tank is the best scenario, but that's not always practical; filling the tank to its normal full level is the next best thing.

2. Install some type of fuel-tank vent fitting that has a gooseneck or other design that helps mitigate the entrance of water. These are produced by both Attwood Marine and Perko. Avoid the temptation to plug the vent, which could lead to a buildup of pressure and possibly a fuel leak.

3. Fill up at trusted sources with high fuel turnover to ensure the least amount of water possible.

4. Don't try to fix a phase-separation problem with additives — they won't work. Contact a company such as Clean Harbors (www.cleanharbors.com), which can empty the tank and help you start fresh. While any phase-separated water/ethanol will be to the bottom of the tank, don't be tempted to install a drain in the bottom; it's against the law and ABYC Standards. It may sound like an easy fix now, but if it ever leaks, you've created a very bad situation. Additives are helpful if used as directed; consider them more of a fuel conditioner/antioxidant. I now use them all year around in all my gasoline equipment (marine, lawn and garden) in the proper ratios.





Don Casey
He's been one of the most consulted experts on boat care and upgrading your boat for 30 years, and he has been on our BoatUS "Ask The Experts" website for the past 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", a bible among do-it-yourself boaters.

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 diverse 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 that he completely restored, including the hands-on installation of all systems. John is a trusted source for technical information for industry professionals.

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, served in numerous editorial and columnist positions for top marine magazines, and has won seven first-place awards from Boating Writers International and many awards for his technical writing.

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