Saturday, February 5, 2011

Bilge Pumps

     I have a "before" picture of the bilge pumps, discharge hoses, and factory wiring right here:

     There are a several disturbing items in this picture, so we'll take them one at a time. First, if you look just below the steering linkage, 2 through hull bolts are visible, with telltale stains from water leaks dripping down the transom and into the bilge. These are 2 bronze bolts that extend through the hull, and mount the transom zinc anode. They were both loose, and in dire need of re-bedding. I had to remove them with a hacksaw, since the nuts were so corroded. These should be examined at every haul-out, and replaced when necessary. Don't take chances here - they are below the waterline.
     Next, look at the wiring for the bilge pumps and float switches. Two of the loom clamps are broken, and the wiring hangs down in the bilge water. This is a very common source of stray voltage, and associated corrosion, in smaller boats. Usually, the insulation is compromised somehow, either at the connections, or the insulation itself begins to crack. Once the wiring is below the water level, battery voltage can be applied to the metal fittings in the vicinity, resulting in rapid deterioration. All bilge wiring should extend up from the respective device, and be securely loomed to stay well above the potential high water level in the bilge.
      The hoses are thin wall, cheap, and corrugated. Corrugated hoses reduce the pump flow rate, by inducing turbulence into the discharge water, along the walls of the hose. This turbulence reduces the effective diameter of the hose. Probably not something of much importance when the pumps are just emptying a little washdown water, but it could mean the difference in a bad situation, so why not change to improved hose, when the time comes?
     Finally, the bilge is loaded with pine needles, leaves, and oil soaked dirt. When I removed the pumps, both strainers were half clogged with debris, and some of it had found its way into the impeller blades and pump volute.
     So, once the bilge was cleaned and repainted (see the December 12, 2010 post), I began rebuilding the pumps and float switches. The switches are easy - just invert them, and clean with soap and water and a suitable brush. Make sure the strain relief grommet, where the wires come out of the switch, is present and snug. If not, replace it. Remember that many earlier float switches were Mercury filled, so be careful with the float, and don't break it. If it is compromised, discard the switch in accordance with local codes, and get a new one.
     The pumps are pretty simple too. Mine are Rule 1500 gph models, which are the stock pumps from Sea Ray. I removed the screws from the bottom of the housing, and cleaned the pump thoroughly. There is an O-ring seal where the pump slides into the plastic housing, so make sure it is clean and properly seated before re-assembling the pump. I bench tested each pump after cleaning, and they both ran smoothly.
     Once the paint had fully cured, I installed the pumps and float switches, replaced the zinc anode bolts (they are bedded with polysulfide), replaced the two badly corroded bonding wires, and rewired the pumps.

     It is hard to see with the small pictures, but the wiring is loomed to the starboard stringer every 6 inches, and the wires gently descend to the pumps and float switches. The hoses are spiral wound smooth bore PVC, 1 1/8" ID. I routed the hoses differently than Sea Ray, by taking them up higher, and securing them directly to the underside of the deck. It is always good practice to route any through hull hoses, near or below the waterline, as high as possible, to prevent water intrusion under adverse conditions. The picture here is not the best, but does show how the hose is immediately routed up, to prevent it.
     So, the pumps are in, and tested well. Note that the upper float switch is also connected to a high water alarm, so if the water gets that high, the audible dashboard buzzer should activate. If it does not, find out why - sooner rather than later. I'll try to post the new wet bar fixture installation tomorrow...

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