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Bent Prop on V Drive?

Discussion in 'Technical Discussion' started by Kitsmark, Jun 28, 2009.

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  1. Kitsmark, Jun 28, 2009
    #1
    Kitsmark

    Kitsmark New Member

    Joined:
    Jan 24, 2009
    Messages:
    15
    Location:
    Vancouver, BC
    Hey guys

    Unfortunately I bottomed out a few weeks ago on a sand bar. No rocks or anything, just sand. The props only spun in the sand for seconds, but I think that was enough to bend the port one.

    I went out yesterday for the first time since and I noticed a small vibration on the port side, while trying to get on plane the port motor started to spin at around 2500RPM, just like a cavitation. The RPM's would jump up, then grab one I pulled back. The vibration stays the same, doesn't get worse. So I am guessing I bent a prop or maybe broke a blade? I doubt the shaft bent since it is tucked up pretty hi into the tunnels.

    Unfortunately where I am moored there is 0 visibility so I can't dive it to see, its going to have to get hauled. I was thinking of being pro active and trying to find a replacement prop to switch while it is up - is there a standard prop for my boat? 1994 Chris Craft 380 Continental with 7.4L Volvo's and weighing in at 15000lbs?

    Thanks in advance for the advice.
  2. Capt J, Jun 28, 2009
    #2
    Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    14,530
    Location:
    Fort Lauderdale
    It is entirely possible to bend the shaft if the props bottomed out, because the props are attached to the shaft. It is highly likely you have bent the propellor and possibly the shaft. Being that the motor is spinning up and the boat is not moving foward, you could have either stripped the keyway on the propellor or damaged the transmission and it is slipping with a heavier load on it. I would recommend getting a photo tachometer and checking the rpm's on the shaft at different motor rpms (such as 1500 rpm,s 2000 rpms, 2500rpms and 3000 rpms, and higher) and recording the readings and then multiplying the readings by the transmission's gear ratio to make sure the transmission is not slipping....... for example if the motor is at 2000rpms and you have a 1.5 reduction (gear ratio) the shaft speed should be 1,333.33 rpms