brass propeller

[irwinsailor]

I have a brass propeller on our boat. When I bought the boat I was only thinking of freash water. I now understand that brass is not the best choice for use in saltwater. How long will a brass prop last in saltwater?

[Jentine]

Are you sure it is not bronze? I know of no manufacturer of brass propellers for marine use.

[irwinsailor]

It is not bronze. I may have some age on it. It was new when I bought it but if I remember right it was several years old. It is brass and I think it is a Michigan wheel.

[CaptainK]

Only thing made of brass for a boat is those bells. And some of the edge pieces for the portholes.

Brass propeller? First time I heard that one?

[irwinsailor]

Very common on the great lakes. I have had several.
I will ask the question in a different way....

IF I had a brass propeller how long would it last in saltwater?

[delmarrey]

I've seen'm in the gift shops

[CaptainK]

[irwinsailor]

BOY ! This sure turned into a hot topic!

[Alan Wheeler]

OK, no problem. Brass, although not the best, will still be OK in Salt water provided you have anodes. Keep the anodes in good condition. You would be best to borrow one of those galvanic meters and make sure you are on the plus side of protection for Bronze metals. I suggest you take an electrical cable (lightweight battery cable) and attach it to rudder stock. Then an anode on the end of it pdropped in the water. Add anodes till the reading is on the strong side. Then replace them as they erode. You may find they erode a little sooner than you would have thought.

[irwinsailor]

I have two zink anodes on the prop shaft at this time. They are in good condition now. Zinks last a long time in fresh water. I understand that salt water is much different. I am glad to hear that my prop will have some life in salt water.

[ssullivan]

Yup... I check zincs yearly in these cold, less salty northern waters. As you head down south, you probably need to keep an even close eye on them.

So when do you leave the Great Lakes, Gunner?

And what route will you take? I just did the Lake Michigan to Huron to Erie to Tonawanda, NY to Erie Canal to Hudson River route in August.

Looking back, it was sure an unusual experience for me. I'm used to sailing on the ocean, not putting around in a ditch. ha ha

The worst part is the exercise paths next to the canal. Runners actually PASS you. Not great for morale. ha ha ha

Nice stops along the way, and free tie ups with H2O and Power!

[irwinsailor]

Sean, We are planning to leave in June of this year. At this time we are taking the same route as you did. I like the free tie ups too.

[BC Mike]

The book you need is called Metal Corrosion In Boats by Nigel Warren. His terminology may be different but this is what the book says. Manganese bronze is perhaps the most widely used alloy for propellers. Since it is not actually a bronze but a brass, it is liable to dezincification. Zinc anodes on the shaft will more or less control this type of corrosion. Manganese bronze is not very toxic to marine life and the decision to paint the propeller with antifouling is borderline.
Michael

[irwinsailor]

It looks like I have my answer. Now I will need to find someone to go down and add a zink every couple of months.

When iron is added to brass it produces hard, tough alloys. One of these is delta metal ( 55% copper, 41% zinc, 1%–3% iron, and fractional percentages of tin and manganese, ) which can be forged, rolled, or cast and is used for bearings, valves, portlights, and ship propellers.
Bronze is an alloy of copper,tin, zinc, phosphorus, and sometimes small amounts of other elements. Bronzes are harder than brasses. Most are produced by melting the copper and adding the desired amounts of tin, zinc, and other substances.
The properties of the alloy depend on the proportions of its components. Aluminum bronze has high strength and resists corrosion; it is used for bearings, valve seats, and machine parts. Leaded bronze, containing from 10% to 29% lead, is cast into heavy–duty bushings and bearings. Silicon bronze is used for telegraph wires and chemical containers. Phosphor bronze is used for springs.
(borrowed from njscuba.net)
here is a chart to help.

Bottom line is, bronze is stronger, brass is just as corrosion resistant. IMHO, run it until it starts to fail, and replace with bronze.