Prop lip wobble

jimmyneutron

Cadet
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Sep 1, 2015
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15
Hi,

Recently I hit some rocks in shallow water while planing at 25mph, the props were totaled. Lost 2/3 of one blade, and chipped the other blades. Engine gave an overheat alarm for a while don't know why, but it stopped. I purchased a new prop afterwards.

The question at hand is, whether my prop shaft needs replacement. I measured the shaft runout with my dial indicator, it's about 5 thou just before the splines in the middle of the shaft. I can't see any wobbles.

However when I installed the new prop, I can see the lips of the prop (rear-most central part) wobbles a bit when I turn the prop by hand.

Help is appreciated.
 

alldodge

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Mar 8, 2009
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Hi,

Recently I hit some rocks in shallow water while planing at 25mph, the props were totaled. Lost 2/3 of one blade, and chipped the other blades. Engine gave an overheat alarm for a while don't know why, but it stopped. I purchased a new prop afterwards.

The question at hand is, whether my prop shaft needs replacement. I measured the shaft runout with my dial indicator, it's about 5 thou just before the splines in the middle of the shaft. I can't see any wobbles.

However when I installed the new prop, I can see the lips of the prop (rear-most central part) wobbles a bit when I turn the prop by hand.

Help is appreciated.

Not seeing what your seeing, but if you can see a wobble, you have a wobble which is much greater then .005 ths. Your going to need to repair the shaft or replace the lower end IMO
 

jimmyneutron

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Sep 1, 2015
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The interesting thing is, I measured my shaft with a dial indicator and it's 5 thou of runout. I also don't see the shaft wobble when I turn it by hand. However when I put on the prop and turn it, I can see the prop wobble. Is it more likely that the prop is defective, or that the shaft has bent?
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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measure the shaft at the vary end.

however some prop hubs are just not round.
 

jimmyneutron

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Sep 1, 2015
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How do you use the dial gauge to measure the end? Because the end has threads, the dial gauge would fluctuate due to the threads?
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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there should be an undercut at the end of the threads, measure that. or measure the major diameter of the splines.
 

Starcraft5834

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Jun 2, 2013
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measure the shaft at the vary end.

however some prop hubs are just not round.

+1 what Scott said.....

Also, with the prop on, look on the end of the prop shaft (it sticks out beyond the prop nut) in the very center you will see a milled hole about a 2mm in dia.. that's the center.. spin the prop and keep your eye on that "milled dot". it should not wobble much....if it does, it's bent.... if it does not wobble, the shaft is fine and your prop collar is not round and balanced.. as Scott said....that problem is common
 
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jimmyneutron

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Sep 1, 2015
Messages
15
I measured the runout at the end of the shaft, it's 7.5 to 8 thou. Is this within acceptable range of runout? I would think that 8 thou would not show up as a visible wobble.
 

alldodge

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I measured the runout at the end of the shaft, it's 7.5 to 8 thou. Is this within acceptable range of runout? I would think that 8 thou would not show up as a visible wobble.

I would agree, you were probably OK all along, that's why I mentioned that I'm not seeing what you are
 

Watermann

Starmada Splash of the Year 2014
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Jan 12, 2013
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I got a brand new Turning point hustler prop that was not perfectly round and looked like it wobbled when you spun it by hand. It was one of the replaceable hub assembly types and the shell was sort of oblong. So that is definitely possible with your new prop.
 
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