How-to

Reading my colleague Lenny Rudow's piece yesterday entitled "Installing New Bilge Pumps, Read This First" made me think of an on-going issue with bilge pumps and any small motor circuit you install on your boat, macerators, bilge blower fans and such. The issue is called "locked rotor" and what happens when this occurs. A locked rotor situation is basically defined as a motor that's trying to turn, but can't, for whatever reason. In the case of a bilge pump motor any bit of debris that enters the motor housing around the pump's impeller and wedges itself between the motor housing and the impeller could jam the pump so that the impeller can't turn. The problem is, your float switch doesn't know that. When the float reaches its turn on point, its still going to send power to the bilge pump motor. what happens next is the tricky part. The motor has power so its trying to turn but can't. So what happens electrically here is the interesting part. You have a voltage source, and a device trying its best to function. It does the  only thing it can do at this point, generate heat. In fact maybe even enough heat to catch on fire. The electrical current is flowing, but gets reduced based on one of the key electrical equations we have, Ohn's Law. Ohm's law states that if voltage is a constant and electrical resistance increases, amperage must go down or be reduced. That's whats happening here, the voltage supply is pretty steady from your battery, the motor is heating up and that increases electrical resistance, amperage goes down. Its a mathematical fact. The problem is, we would hope a fuse would blow in this case and shut down the power to the motor. It won't. Why? Because fuses blow based on amperage and if the fuse is not being subjected to enough amperage, its just going to sit there and allow whatever current there is to flow freely. The simple answer to this problem is to be absolutely certain the fuse for your bilge pump motor is rated exactly as the motor manufacturer recommends and that's where the installations typically go wrong. The vast majority of blower fan and bilge pump circuits are over-fused, and in the event of a locked rotor will not blow! In the photo below, you see the beginning stages of what can happen. Mind you I disconnected the power to this motor after about 20 minutes.    If you turn sideways and look very carefully at the printed information on the top of the pump you'll see that Rule recommended using a maximum 11/2 amp fuse (this one is a 24 volt motor). All I did to get the melt down going was lock the motor impeller in a vise and install a 5 amp fuse. Again, within about 20 minutes the case got hot enough to start melting as you can see. Had I left the power connected, it would have eventually caught on fire. So, besides Lenny's sage advice about adding a vented loop to your near the waterline bilge pump installations, make sure the fuse you use matches what the pump manufacturer recommends, and no more. …Read More

The view from next door. © Clipper Ventures Donna Womble was very clear on her reasons when she signed up for leg six of the Clipper Round the World race. She was a lifelong sailor, she wanted some sea time, it just wasn’t happening, and this would solve the problem. Leg six is scheduled to [...] …Read More

Editor’s Note — Victoria Allman is the chef aboard a 143-foot megayacht and the author of the recently released “Sea Fare:  A Chef’s Journey Across the Ocean.”  This is the third in a series of periodic columns here on OceanLines featuring her irresistible recipes. Best of all for OceanLines readers, who are travelers of the [...] …Read More

href="http://www.pulsetech.com">www.pulsetech.com …Read More

Fair to say, many a lifelong sailor has never experienced 24 knots on a boat. Also fair to say, it takes a lot of 30-plus to turn out an average like that while logging 28,523 miles. On a new circumnavigation record. Which will, however, be computed for official purposes using, not the actual distance sailed, [...] …Read More

How crazy are the French about long distance adventure sailing? Crazy enough that photographer Yvan Zedda could get a plane ride and a picture to be captioned thus: Flyby of the maxi trimaran Groupama 3 to the NE of the Azores aboard a Falcon 50 fleet 24F from the Naval Air Base of [...] …Read More

Mobile Mariner LLC has announced the official launch of the Mobile Mariner™ for the Blackberry® smartphone, which will provide NOAA marine weather forecasts, tide information and life weather conditions for the coastal United States, including the Great Lakes. More upcoming releases will expand the application to other smartphone platforms and cover more international areas. Mobile Mariner [...] …Read More

KVH Industries said today that it will offer rebates up to $200 through the end of April on its TracVision M1 and M3 satellite TV systems.  The M1 and M3 systems are typically used on smaller boats, although the M3DX unit, with its HDTV capability could easily serve as the workhorse on almost any size [...] …Read More

Well we're finally getting a break in the weather here in Rhode Island and people are beginning to uncover their boat's and start an early spring assessment of work to be done. This made me think about some things you need to be looking for on your boat, today in the electrical area. One of the advantages of being an industry insider is that some of us trade horror photos of things we see. Today I want to share with you one photo that came in from Derek Rhymes, the principle at All Boat & Yacht Inspections LLC, a marine surveyor in Annapolis, MD. This particular photo holds a dear spot in my shop of horrors collection and represents the sort of thing you need to be making sure does not exist on your own boat. Scenes like the one below could be the cause for some truly shocking experiences on board. What you are looking at is a commonly used marine water heater. It is powered by the shorepower system and the power is supplied by the three wires you see in the center of the photo. Black, white and green represent 110-Volt service. Notice how the wires are routed through a stamped out hole on a metal bracket extending outward from the case of the heater. The stamped out hole has no chafe protecting grommet around it's perimeter and let me tell you, the edges of that hole are sharp! The wiring is laying on the sharp edge. What will ultimately happen here is that due to normal vibration on the boat, the edge of the metal is going to chafe through the wire insulation and create a short circuit. If the boat owner is lucky, it'll be a really good connection and trip the circuit breaker protecting the heater circuit. If the boat owner is unlucky, the short circuit will have a poor quality connection and although leaking current directly to the case of the heater, the connection will not be able to carry enough current to trip the breaker. So, the short circuit will just quietly wait for the boat owner to reach down into the locker where the heater is installed. As soon as the boat owner touches the case of the heater. ZAP! Electric shock. The moral of the story here is to visually inspect your wiring system and add chafe protection whenever you see a situation like this on your boat. Don't wait to get zapped! …Read More

Do you really need to update your electronic charts, and the chartography in your chartplotter’s brain? A three year old unit, for example, may seem plenty “new.” Unfortunately, the Coast Guard has this pesky habit of moving nav aids. Worse yet, Mother Nature has this pesky habit of moving sand bars, shoals, and inlet channels. [...] …Read More