Brass Shaft Brush Connected to Metal Hull Does this Really Work?

We received a good query from reader Gerry this week that is worth sharing a bit of discussion on. The photo he sent in is on his aluminum hulled sailboat. What you see in the photo is a flat brass bar that someone applied some solder to (the grey stuff at the end and rubbing against the prop shaft). The other end of the brass bar is simply screwed to the aluminum cross piece you see running under the shaft. The brass bar gets bent up and is rubbing against the propeller shaft. You can see where it has been rubbing against the shaft as it spins.

So, what is this all about anyhow? The concept here centers around bonding of the shaft to the hull for the purpose of mitigating corrosion. The idea is that propeller shafts really don't make a very good electrical connection to the rest of a boat's bonding / cathodic protection system since the propeller shaft is connected directly to the transmission (reverse gear) at the back of the engine. Electrical continuity through the transmission is always a bit dicey, especially when underway. So, how do these shaft brushes do in this situation? Usually not too well frankly. Most of us that deal with matters of marine corrosion don't actually recommend them. The failure rate for these brushes, and especially something as jury rigged as the one in the photo above is just too high. I've checked many of these over the years for electrical continuity and found an open circuit between the shaft and the brush.

So, what's the answer here? Simply provide adequate shaft anodes to protect the shaft and propeller for a reasonable amount of service time and treat any other underwater metal you wish to protect separately with additional anodes as needed. Most of these shaft brushes are just going for a ride on the boat they're installed on and really not contributing much to help in the corrosion protection area.

Its the time of year when we start getting the covers off our boats and start that annual spring clean-up and maintenance routine to get ready for a summer of fun on the water. With that in mind, let me just share with you all one of my biggest fears about boating. Its called the single point failure. Now some of you with engineering backgrounds probably know exactly what I'm talking about here.

A single point failure is something where if only one thing goes wrong something really bad can happen. It brings me way back in time to a point where my uncle talked me into going flying with him in a single engine airplane. After we got up to about 1000 feet in the air I asked him what happened when the engine quit...

He assured me that was very unlikely and that even if it did, he'd do his best to glide the plane back to earth. Honestly, I wasn't totally reassured. Well, let's just say I spend as little time as possible in single engine airplanes. Can't say that about boats though and some of my friends probably think I'm crazy when I talk about going 30 or 40 miles offshore in a single engine boat. I do it all the time, but understand that I really pay super close attention to anything on the boat that could cause a catastrophic single point failure. So, consider the photo here:

One bolt. If it breaks or falls out, the steering is gone!

I took this shot on a tour boat my wife and I were riding on in the Everglades. The boat wasn't too fast, maybe 10 or 12 knots, but we were moving through a rather narrow channel that had all manner of creepy insects and gators just waiting for someone to fall in the water so they could do their thing. The bolt is clearly loose and is not secure with a locking nut. As our driver was working the helm, I could see the bolt working in the hole on the steering arm of the outboard engine this rusty little mess is connected to. If the bolt falls out or breaks we will have a single point failure that will cause the complete and rather instantaneous loss of steering on our boat load of happy, innocent tourists. I didn't say anything to anybody until we got back to the dock safely and then I mentioned it to the captain. He probably thought I was some kind of nut and ignored me.

Its OK, but rest assured I think about things on boats that if just one thing occurs, something really serious could happen. You need to start thinking that way too. Spring is the time to go over your boat with a fine eye for detail looking for things like this. Send in your single point fears and we'll share them with our readers. We need photos too so don't forget to include those as well.

Typical Use of European RCD Devices on US Boat

Blue Sea ELCI Set Up, Easily Retrofitted

North Shore Safety Unit Available through Marinco, 30 and 50 AMP Service

Our recent entry discussing ELCI devices got a new query on the topic from Jim. Here it is:

"Ed,
I'm trying to make sense out of the ELCI/RCD stuff. Very difficult. n the marine marketplace, what's actually available? Blue Sea Systems seems to have units available now. The Hubbell/North Shore/Airpax-Sensata/Techsol solution does not seem ready to go yet. Blue Seas is physically large. Hubbell/NS/Sensata is better. Legarnd and the EU solutions appear to be a current transformer and breaker in a single unit. Based on your experience and your industry knowledge, can you provide a list of manufacturer's and products that are actually available and meet ABYC, E-11, 2012 for retrofits - *not* new construction - retrofits to existing boats, as of 1Q2013?"

The bottom line here is that the newest version of ABYC E-11 standard that addresses this whole ELCI device issue is very open at this point to allow a variety of products that are indeed available to be used. To quote E-11 directly it now states:

An Equipment Leakage Circuit Interrupter (ELCI) or Type A Residual Current Device (RCD) shall be installed with or in addition to the main shore power disconnect circuit breaker(s) or at the additional overcurrent protection as required by E-11.10.2.8.3 whichever is closer to the shore power connection.

EXCEPTION: Installations where an isolation transformer is installed within 10 feet (3 meters) of the shore power inlet or the electrical attachment point of a permanently installed shore power cord and supported according to 11.14.6.3

"11.11.1.1 The trip level shall be a maximum of 30mA. The trip time shall be a maximum of 100ms.

11.11.1.2 This device shall meet the requirements of UL 1053 Standard for Safety for Ground-Fault Sensing and Relaying Equipment and the requirements of UL 943 Ground Fault Circuit Interrupters with the exception of trip level and trip time, or

11.11.1.3 IEC 61008 Residual current operated circuit-breakers without integral overcurrent protection for household and similar uses or IEC 61009 Amendment 1 - Residual current operated circuit-breakers with integral overcurrent protection for household and similar uses and IEC 61543 Residual current-operated protective devices (RCDs) for household and similar use - Electromagnetic compatibility

NOTE:

1. Trip levels of less than 30ma and times of less than 100ms may result in nuisance trips in certain environments.

2. If included, the circuit breaker must also meet the requirements of E-11.10.2 Overcurrent Protection.

3. IEC compliant RCD’s must be rated for 125, 250 V 60Hz applications

11.11.1.4 The ELCI or RCD shall be readily accessible."

All of the above parameters allow fairly broad latitude at this point. To my mind the only glaring issue is with 100 amp shore power systems, but I do firmly believe at that point the boat is large enough so that not installing an isolation transformer in the shore power is absolute foolishness. The exception above eliminates the ELCI requirement if said transformer is installed.

So, we are now narrowed down to 30 and 50 amp service considerations. Between Blue Sea and Marinco (Northshore) I think we are covered at both the 30 and 50 amp levels. As for the European gear, I believe a call to Ward's Marine Electric in Ft. Lauderdale will get you what you need.  www.wardsmarine.com

Using your multimeter (DVOM or digital volt ohm meter) to scope out excessive voltage drop. Diagram from one of the author's books, Advanced Marine Electrics and Electronics Troubleshooting

We received a question from a reader the other day asking about how they might go about checking for excessive voltage drop on their boat. Good question that needs a bit of explanation.

First of all, what is voltage drop and why do you need to care?

All of the electrical equipment on your boat is de3signed to operate within certain engineered voltage levels. Electronic equipment in particular is quite fussy about this matter. To that end, the ABYC describes two levels of acceptable voltage drop for on board electrical circuitry. Maximum levels of drop at 3% and 10% are identified. The specific circuits that 3% is allowed at are navigation lights, bilge blower circuits, panel board main feeder cables and mission critical electronic circuits. Its important to note that the standard actually states "electronics". The intent of this is really mission critical as we have since defined. Truth is, if your DC powered AM/FM stereo/CD/IPOD/MP3 player has a bit of excessive voltage drop in its power supply, nobody really cares, and its not going to me life threatening. Your GPS or VHF radio on the other hand, could be a different story. You get the idea.

So, how do you the boat owner actually confirm whether you have too much voltage drop in a given circuit anyhow? Further, how do you actually pinpoint where in the circuit the excess exists?

In the diagram above I illustrate how to use your DVOM or multimeter in a seemingly strange way. Strange in part anyhow. To check for voltage drop simply check at the battery or source of power for a circuit by connecting you meter leads black to DC negative and red to DC  positive and check the voltage. The meter needs to be set to the "DC Volts" setting and an appropriate voltage scale if your meter is not self-scaling. BTW, this all assumes that you have confirmed that your power supply is in good serviceable condition.

OK, once you have determined the voltage at the power source and written down the measured voltage (tens of a volt count here so record that), go out to the appliance in question and measure the available voltage at the piece of equipment.

Now, subtract the voltage value at the device from the voltage value at the source. Next, divide the difference by the measured voltage at the source. Move the decimal point two places to the right and you will have established the actual voltage drop in the circuit. If that value exceeds the allowable percentage value assigned by the ABYC Standards E-11 then the next step is to figure out where in the circuit the excess exists. That's the point where you start using your multimeter in the strange way I mentioned here and as shown by tracing the meter leads in the lower meter illustration above. You'll see that you have one meter lead connected to one end of the conductor in question and the other meter lead connected to the other end of the same conductor. Your meter is going to be set to the DC volts scale. I know that for many of you this seems just plain wrong, but believe me this works. The reading you get on your meter is the actual voltage "lost" in that leg of the circuit. Its going to be a pretty low value, typically in the tenths of volts, maybe even hundredths of volts. but by working your way through a circuit, wherever you get high readings when doing this is simply showing you where the excessive voltage drop may exist in the circuit.

For example, you could check the integrity of a battery cable connection to the battery post by checking between the actual post and the clamp around the post. I high reading indicates a poor quality connection between the clamp and the battery post. In the diagram above, a reading that was too high would indicate a wire that is undersized for the task at hand. Remember these facts relative to voltage drop, excessive drop can be caused by:

• Loose terminal connections.
• Excessive corrosion.
• Wiring that is undersized for the task.

Remember in all cases you must always confirm the integrity of the power source first. A bad battery will give you funky readings.

I'm starting to think of spring maintenance items as my cabin fever sets in. One of the things that most folks totally ignore, don't know about, never have heard of, has to do with anodes (most folks just call them zincs). Not just any zincs, but the ones that may be hiding inside your engine's cooling system. There's a picture of one here that was found hiding in the seawater inlet piping on a Caterpillar diesel I was hired to check out a few years back. In that case the boat owners knew all about their engines zincs and hired me to figure out why the one you see in the photo (skinny grey colored thing in the middle) was consuming itself in 2-3 weeks.......

The bottom line on finding these things? Owners manual? Check with your engine maker and see what online resource they have.... I can tell you their location is NOT always obvious. As for how long they should last, typically through a normal 6-9 month boating season. In the case above, we had a water flow velocity issue and the anodes were being impacted by what is called "erosion corrosion". The water in the raw water intake plumbing was screaming by this anode so quickly it was literally scrubbing it away in a couple of weeks. The fix in this case was a matter of relocating the anode to a place in the system where the velocity of the water flow was significantly slower. All ended well.

So, find your engine anodes and check them out. If you've never seen them, they may actually be gone so you may have to start from scratch with this.