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Maximus throws blade at my SCX

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Old 10-18-2011, 09:14 AM
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He was asking about the cleaver off the Nor-tech.



Got that right Smitty. When Bravo props are semi or fully surfaced, they flex like crazy. They don't when they are run as they are supposed to. A Bravo drive is not a surface drive. If you want a surface drive, buy one that was build as one, that spins real surface props.

Being I am on learning curve like everyone else is or was at one time or another I made a mistake not knowing the out come. I just kept adjusting my SCX till I got great results and it does haul a$$ like it sits but at a cost. Now I know ill have to loose some MPH to keep a blade on it. Thanks to you guys… I know why it did it. (AS I SAID LESSON LEARN)
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Old 10-18-2011, 09:16 AM
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Hering does cast thicker eared props for this reason just in case you wanted to ck them out . good luck
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Old 10-18-2011, 10:07 AM
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Hering does cast thicker eared props for this reason just in case you wanted to ck them out . good luck

And they break blades too.
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Old 10-18-2011, 10:26 AM
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And they break blades too.
And have a massive price tag.
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Old 10-18-2011, 11:01 AM
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at least they have a year warranty if you buy them new .
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Old 10-18-2011, 01:26 PM
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This is what happens when you throw a blade. Water was smooth as glass I was running about 6300 RPMs. Then all of a sudden vibration out of the wazu.
I hope it's a typo. But if you were spinning that prop at 6300RPM's what do you think was going to happen??

Mercury started using higher strength alloys a few years ago. They even had to re-tool because of the hardness of the metals.

When was the last time you inspected your prop? If there was any kind of ding or scratch caused by hitting the prop with a tool, rock, wood, etc., it could have caused a stress point on a blade. Centrifugal force at 6300RPM and it came apart.

There shouldn't be anything wrong with your props as long as they are worked properly (were they repaired?).

Include a visual inspection of the props prior to splashing the boat and check for loose nuts and proper torques on the drives on a regular interval. You would be amazed at what starts to come loose when we run the hell out of these things.
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Old 10-18-2011, 01:50 PM
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I hope it's a typo. But if you were spinning that prop at 6300RPM's what do you think was going to happen??

Mercury started using higher strength alloys a few years ago. They even had to re-tool because of the hardness of the metals.

When was the last time you inspected your prop? If there was any kind of ding or scratch caused by hitting the prop with a tool, rock, wood, etc., it could have caused a stress point on a blade. Centrifugal force at 6300RPM and it came apart.

There shouldn't be anything wrong with your props as long as they are worked properly (were they repaired?).

Include a visual inspection of the props prior to splashing the boat and check for loose nuts and proper torques on the drives on a regular interval. You would be amazed at what starts to come loose when we run the hell out of these things.
That's funny

What are you on about? These props are not meant to be surfaced, stress risers or not. Do you really think the prop was spinning @ 6300? The motor was. The words gear ratio comes to mind. Let's crunch a number for fun. 32" pitch @ 6300 rpm's with 10% slip. 172 mph!!!
The Herings will hold up better, but as with big hp Bravo style drives, it's on limited time.
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Old 10-18-2011, 06:57 PM
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Originally Posted by A.O. Razor View Post
That's funny

What are you on about? These props are not meant to be surfaced, stress risers or not. Do you really think the prop was spinning @ 6300? The motor was. The words gear ratio comes to mind. Let's crunch a number for fun. 32" pitch @ 6300 rpm's with 10% slip. 172 mph!!!
The Herings will hold up better, but as with big hp Bravo style drives, it's on limited time.
Geez, I don't know you, and you don't know me. Your complaining about what I'm on about? I'm trying to help a fellow boater out. Put the bottle down and quit feeling sorry about yourself because I have a bigger boat then you. And it's a FOUNTAIN!


www.mercuryracing.com/propellers/maximus.php Here is a link for maximus propellers. Maximus are designed for high x dimensions, re: surface piercing props. No the prop wasn't spinning at 6300rpm, but if he has a 1.5 gear ratio then the prop was spinning about 4,200 rpm compared to 3,500 rpm if the engine was turning 5300 rpm. If he has a 1.35 ratio the numbers would be 4,600rpm vs. 3,900 at 5,300rpm. Don't know his drive gear ratio.

Point is centrifugal force exponentially increases with increased rotation. Look at his picture close up. On the leading edge of the prop you can see where the separation is at an angle then goes straight across the blade. That looks like where a crack started and the forces ripped the rest of the blade off.

Doesn't matter if it's a boat propeller, an airplane propeller, or a turbine blade. If there is a dent or ding thats not properly dressed out it becomes a stress point and will eventually fail with catastrophic results.

It's not the propeller thats to blame. Just include inspecting your prop just like you check your engine oil prior to starting up.

Cheers

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Old 10-18-2011, 07:36 PM
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Originally Posted by mike38scarab View Post
Geez, I don't know you, and you don't know me. Your complaining about what I'm on about? I'm trying to help a fellow boater out. Put the bottle down and quit feeling sorry about yourself because I have a bigger boat then you. And it's a FOUNTAIN!


www.mercuryracing.com/propellers/maximus.php Here is a link for maximus propellers. Maximus are designed for high x dimensions, re: surface piercing props. No the prop wasn't spinning at 6300rpm, but if he has a 1.5 gear ratio then the prop was spinning about 4,200 rpm compared to 3,500 rpm if the engine was turning 5300 rpm. If he has a 1.35 ratio the numbers would be 4,600rpm vs. 3,900 at 5,300rpm. Don't know his drive gear ratio.

Point is centrifugal force exponentially increases with increased rotation. Look at his picture close up. On the leading edge of the prop you can see where the separation is at an angle then goes straight across the blade. That looks like where a crack started and the forces ripped the rest of the blade off.

Doesn't matter if it's a boat propeller, an airplane propeller, or a turbine blade. If there is a dent or ding thats not properly dressed out it becomes a stress point and will eventually fail with catastrophic results.

It's not the propeller thats to blame. Just include inspecting your prop just like you check your engine oil prior to starting up.

Cheers

I'm not attacking your person, and no, I don't know you. You state in your post, that he's spinning 6300 and therefore he's prop is comming apart. The rpms has nothing to do with it, it's because of blade flex. That is why I wondering what you are talking about. Wether or not he needs to check more often for cracks, I know nothing about.

Oh and my boat is 42 feet, and I don't drink.

Happy boating.
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Old 10-18-2011, 08:32 PM
  #30
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Just my opinion but the labbed props also have a limited life span. I know a few people that after a few years of running them had to 1) send them back to re-pitched or 2) throw them in the garbage all together.
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