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Losing prop blades

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Old 06-22-2004, 07:10 AM
  #11
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Default Re: Losing prop blades

Throttle Up told me the Bravo's are known for this. I wish the Hydro Q4-X's would have had the excellent cruise speeds of the stock Bravo's.
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Old 06-22-2004, 07:16 AM
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Default Re: Losing prop blades

No, I do not think you would feel it until it actaully seperated. You have a lot of distance between the prop and the hull. Every time you go through a gear you dampen the vibration significantly. That is why I mentioned to check everything else in the line shaft etc. There has to be wear on other components, even though not readily visible.

Picture the relationship of taking a coat hanger and bending it until it heats and breaks. This is what Strip's prop may have experienced. That is why there is a crack in the other blade as well. Once one went there is a significant prop imbalance situation.

I have also experienced props getting out of balance just through running. Not NORMAL running but high HP boats producing excessive load through a lot of torque. Slamming the throttles out of hole may actaully bend a prop blade or blades enough to cause this problem. So it could be the way the boat is operated. It only takes once and the damage may be slow wearing and not show up for hours.

I had to have my drives rebuilt last year. The prop shaft splines were twisted like candy canes. HP + a little flying + high RPM's on re-entry = bent or broken stuff.

Last edited by expresscat39; 06-22-2004 at 07:33 AM.
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Old 06-22-2004, 07:57 AM
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Default Re: Losing prop blades

better take a look at who does your props...also, I WOULD, FOR SURE take that drive down and inspect the gears!...prop imbalance w/o loosing a blade can cause drive failure.

props do not go out of balance unless metal has been added or taken away...however they do fatigue and blades can change individually, most of the time gaining pitch...a drop in RPM is a tell tale sign of this...
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Old 06-22-2004, 08:11 AM
  #14
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Default Re: Losing prop blades

I've got the opposite proplem, one of my Merc. cleavers is off by 300 rpms, and is noticable getting on plane as well as anything after 3500 rpms, they are going back today.

I Had The Same situation on breaking blades on my Herrings on Radio Active, twice, it can be very dangerous with someone behind you, and thanks for the reminder, I'm still waiting (1 year later) for the replacement props.

Last edited by JASSMAN; 06-22-2004 at 08:25 AM.
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Old 06-22-2004, 08:11 AM
  #15
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Default Re: Losing prop blades

in one of the pic's it looks like the corner of the lifting strake is in the wake shadow of the prop. this would be an area of little or no water for the prop to grab, this would cause the prop blades to flex from that point out excessively.
when i ran spinnelli props they would break at the root of the blade after 45 min's , went to mazco's props and they are still fine today. just more food for thought.
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Old 06-22-2004, 08:14 AM
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Default Re: Losing prop blades

"in one of the pic's it looks like the corner of the lifting strake is in the wake shadow of the prop. this would be an area of little or no water for the prop to grab, this would cause the prop blades to flex from that point out excessively."....incorrect statement
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Old 06-22-2004, 09:21 AM
  #17
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Default Re: Losing prop blades

Are these stock or have they been thinned?
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Old 06-22-2004, 05:56 PM
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Default Re: Losing prop blades

it happens ,by looking the props are new. Send it back to Mercury and they will replace it. When we lab finish these props not all but some have casting holes open up. This is caused by air pocket in the casting and when put under tremendous stress it will break.This is called Fatigue.
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Old 06-22-2004, 06:09 PM
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Default Re: Losing prop blades

Would cavitation cause this? You mention a high X. Doesn't cavitation create heat? Just a thought.
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Old 06-22-2004, 06:15 PM
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Default Re: Losing prop blades

cavation is like boiling water,yes it creates friction which results in a higher temp.running this prop high in and out of the water will cause the fatigue.Or so to say BLADE FAILURE.
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