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Old 05-10-2010, 05:50 PM
  #1
71dartswinger
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Default motor mount

this is the second motor mount that has broken on Logans airboat
this is 1/8" aluminum angle the first was exactly the same break.
built new ones out of 1/4" plywood
the engine is only a Fox .25 bbs
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Old 05-10-2010, 07:04 PM
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RS 38-40
 
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Default RE: motor mount

Looks like a vibration problem . Maybe the prop is out of balance .
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Old 05-10-2010, 07:45 PM
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71dartswinger
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Default RE: motor mount

its only the one side that breaks (from front of boat its right side)
the motor has been changed from this picture from OS.20 to Fox .25
had no problems with .20 other than fuel/oil leaking out of front of crank and around strap on exhaust

checked prop balance its fine but i think plastic spinner is out of balance has different size screws
going to pickup metal nut spinner
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Old 05-13-2010, 08:15 AM
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Default RE: motor mount

If you did'nt use a break to bend the aluminum chances are the bend area is full of small cracks that will cause the piece to break with the vibration from the engine. To bend aluminum without the weak areas you have to use the right radius for the thickness of the metal. Someone on here will be able to help with the problem. Dennis
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Old 05-13-2010, 02:56 PM
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71dartswinger
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Default RE: motor mount

its 1/8"x1"x1" angle i bought at lowes
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Old 05-13-2010, 06:46 PM
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RS 38-40
 
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Default RE: motor mount

One thing you might want to look at when you make another mount is that the holes are not oversize and that they are lined up with the motor holes . It also might help to add a doubler under the motor to give it a little more meat . The angle you are using is not usually very hard and any movement will elongate the holes and put more stress on the mount . A prop doesn't have to be out of balance much to cause problems .
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Old 05-13-2010, 08:15 PM
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71dartswinger
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Default RE: motor mount

borrowed a prop balancer from a guy at work and prop is out of balance
got where it will stay horizontal but put vertical it is out of balance.The center hole is not centered.
bought new prop and spinner today and balanced it .
the holes in aluminum were the same size as the ones on motor
and the bolts were still tight . the break line follows the edge of the motor mounting flange
like i said this is the second one broken. mount now is 1/4" plywood
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Old 05-16-2010, 10:18 PM
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Default RE: motor mount

place a thin strip of wood or even better, rubber between the engine and the aluminum
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