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View Full Version : Crack in Stainless Prop. Help!



Greg Maier
08-18-2002, 09:49 PM
Today, while examining my Blackhawk Props, I noticed a 2 inch long crack that starts at the leading edge of the blade and runs parallel to the shaft. Can Stainless props be repaired by welding or is the prop ruined?

Donzi Blackhawk
08-18-2002, 10:49 PM
Greg,

Give Sarasota Hill Propeller a call to see what they think. It sounds as if you may have to spend a little to save a lot. If I'm not mistaken one of our board members "Blackhawk" lost a blade on one of his props. When this happened, gears in the drive were stressed. He had to rebuild the drive. If it were my boat and the prop could be repaired, I would use it only as a spare. Buy a new one and have the peace of mind that it won't let loose.

Bryant

Woodsy
08-19-2002, 06:37 AM
You need to get a new set of props... It kinda sucks, but where you are describing the crack, you really cannot weld it and have it hold together for very long. A set of props is far cheaper than a rebuilt outdrive and a set of props....

Woodsy Von Donzi :D :D

blackhawk
08-19-2002, 08:18 AM
Yep, that's exactly what happened!!! I called a few places (York, Sarasota Hill, etc) and they said that a cracked prop can fixed. They cut metal out, weld in new and rebalance. Obviously, I have know idea how strong it would be be everyone I talked to seemed confident it would be very strong. Just passing along what I was told.

Scott

Greg Maier
08-19-2002, 05:24 PM
Update on the Cracked Prop: Found a new set of 31p Blackhawk props today for $799. Pretty reasonable, so I got them. I called Mercury Racing about the cracked props and they said that they can be fixed by cutting out the crack and welding in a new piece, but, the props usually recrack at the welds. Mercury said that since these are surface piercing, they go through a complete load and unload cycle at every rotation. This puts tremendous stress on the prop. The most likely scenario was that I had a little nick in the prop and this formed a stress riser. The stress riser eventually turned into a crack from the numerous loading and unloading of a surfaced prop. I've learned my lesson.

blackhawk
08-19-2002, 05:45 PM
Greg, glad to hear you got some 31's. You should be able to pick up a couple mph with them. I would get your cracked one fixed for a spare.

Gary S.
08-20-2002, 05:25 AM
Your prop CAN be welded, done correctly, the weld is stronger than the base metal. The problem with welds failing is the guy under the hood, if it looks pretty they are happy, and there is more to it. For starters, the entire thickness of the metal has to be welded, meaning you grind a 37 degree bevel, then there has to be a gap between the two pieces so there is total fusion. If you don't fuse them completly you have left a crack allready started. Stainless also needs an argon purge inside and out of the weld, or else it will oxidize and thats another crack allready started. I have yet to find a "prop shop" welder who has a clue about any of that. If you have a hard time finding someone who is confident of making the weld, I'll do it for you. You just pay the shipping.

Greg Maier
08-20-2002, 08:31 AM
Gary,
I'll take you up on that offer ! My Dad is a
retired mechanical engineer and he also said that a proper weld will actually be stronger than the
original. Unfortunately, he doesn't have a welding machine. My Dad also told me that the grade of stainless is an important factor in the weld. I will call Mercury and find this out.
Thanks
Greg

Gary S.
08-20-2002, 04:15 PM
Greg, I'll e-Mail you my address. I have 308 and 316 wire to use. Your dad should be able to verify the quality of a heli-arc weld. Just so we are clear,, I'll I'm doing is the weld, check with your prop guy to see how much metal he wants on the cover or if he wants me to flat top it. Better yet call me at home,,, 724-643-2045 anytime after 5,,, today is fine ,, tomorrow is the Creed concert so you won't catch me then.

blackhawk
08-20-2002, 09:18 PM
A "good" weld is like a broken bone, stronger than original. The key word here is "good". Sounds like Gary know his s**t!

ClassicRazorback
08-21-2002, 12:30 AM
Would the blade you weld on be more brittle than the others? I would think it needs to be anealed (sp) so the vibration would'nt tear it up.

chris

Gary S.
08-21-2002, 05:10 AM
Classicrazorback, to answer your question, stainless is very brittle to start with and the trick to making a good weld is using a higher grade filler to replace alloy's that are "burned" out and not overheating the metal. The only way to tell if you have a good weld is to see the color before it get's wire brushed, if it's black it's junk and burned up if you see shades of blue and strawberry red, thats a good one.

MOP
08-21-2002, 08:27 AM
I have heard of re-baking bronze wheels to get the proper temper back, does that apply to S/S wheels.