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Dr. Kurt Michaux

Can anyone tell me if stainless props get stress fractures as described in mssg....

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Hey there.......

Was wondering if anyone could tell me.........I had someone looking at my boat the other day to purchase it and the person looking seemed to be a very nice gentleman, but I am curious......He said my prop had a stress fracture in it.  It was approximately 4 inches long and looked like a piece of string, but it was rust.  The prop is stainless steel that came on my Yamaha 225 HPDI/Ranger Z20.  Since I have no knowledge of these things, I didnt know what to say.  It was running front to back on the main part of the prop, not the blades..........it didnt start or finish at the end and didnt go all the way through to the inside.  Since I deal with human bones as a profession and see many fractures, that seemed to me to be not possible to fracture that way, but I dont know stainless steel............any opinions or suggestions.

thanx

kurt

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Metal can do funny stuff. I have a friend that is a machinist and he says the imported stuff is very different in quality when performing machine work. A lot of the imported steel he says is really brittle like cast iron. One needs to remember that metal as well as a lot of other things is used in applications where it is supposed to give and take. Brittle sure sounds like a bad quality to hear about. That being said, anything is possible. It sure sounds more like someone tire kicking and reaching to find faults in your boat. Since it is your boat, I would say you would know the history enough to know if anything was ever struck to cause such a thing. A pic would be interesting to see.

now that I think about it, a trip to a good machine shop and a little test called magnafluxing would eliminate your concerns.

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Metal can do funny stuff. I have a friend that is a machinist and he says the imported stuff is very different in quality when performing machine work. A lot of the imported steel he says is really brittle like cast iron. One needs to remember that metal as well as a lot of other things is used in applications where it is supposed to give and take. Brittle sure sounds like a bad quality to hear about. That being said, anything is possible. It sure sounds more like someone tire kicking and reaching to find faults in your boat. Since it is your boat, I would say you would know the history enough to know if anything was ever struck to cause such a thing. A pic would be interesting to see.

now that I think about it, a trip to a good machine shop and a little test called magnafluxing would eliminate your concerns.

You mean a penetrant test(stainless steal)?

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Sounds like a possible electrolysis mark. Does the boat stay in the water at a dock? Have you used it in salt water? Have you used it on the upper St. Johns? I doubt that it is a stress anything.

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Thanx everyone for all the great answers.......

Sounds like a possible electrolysis mark. Does the boat stay in the water at a dock? Have you used it in salt water? Have you used it on the upper St. Johns? I doubt that it is a stress anything.

never been in salt, st johns or anywhere near it....never left it in water either......what is an electrolysis mark?

thanx again,

kurt

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Without getting complicated, it's what causes galvanic corrosion of metal parts of the motor when it is in an area where electricity is present in the water.

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When I referred to magnafluxing I was also saying i felt you had nothing to worry about. If you have any memory of instances that could have caused damage, it might be wise to have it checked out. most reliable machine shops can do this test. I attached a link to better describe it. Personally, I think the guy was jerkin your chain trying to beat you out of $$$$

magnafluxing link

http://www.circletrack.com/techarticles/139_0308_magnetic_particle_inspection_tech/index.html

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I run a Mercury Tempest Plus on a 225 Yamaha. Several years ago(about 5 yrs) I noticed what I thought were stress cracks in the hub of my prop.(none were 4 inches long). I removed the prop and took it to a local prop repair shop. They told me it was from the manufacturing process and I had nothing to worry about. I am still running that prop without incident.....................Al

PS- If you have a repair shop available you may want to have it inspected.

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