Vibration |
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dutch-us
Newbie Joined: August-19-2022 Location: Western Michiga Status: Offline Points: 12 |
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Posted: November-21-2022 at 2:05pm |
I have a 1968 Mustang C/Craft with a POLY 318. When hard throttling to pull up a heavy skier, it vibrates terribly. Once cruising, not bad. I have aligned the propeller shaft and even installed mufflers. The engine runs great.
Any ideas?
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68 Mustang Wes
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21104 |
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Junk prop or bent shaft are the 2 biggest sources of vibration.
Misalignment will dampen vibration, not exacerbate it. How’s the strut bushing? |
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Jonny Quest
Grand Poobah Joined: August-20-2013 Location: Utah--via Texas Status: Offline Points: 2822 |
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Tim hit the main ones: 1) bent shaft; 2) strut bearing; and 3) unbalanced / damaged propeller.
You can check for "play" of the shaft in the bearing by wiggling the prop side-to-side and verifying movement of the shaft in the strut. How old is the prop? Has it been hit and "fixed"? Maybe post a photo of the prop (include the hub). You can measure for a bent shaft easy enough while the shaft is on the boat. You need a dial indicator and then attach the base of the dial indicator onto the strut. You want to check the shaft just aft of the strut. Can you provide a bit more info on your shaft alignment? JQ
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2003 Ski Nautique 206 Limited Previous 2001 Ski Nautique Open Bow 1994 Ski Nautique Open Bow Aqua skiing, ergo sum |
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dutch-us
Newbie Joined: August-19-2022 Location: Western Michiga Status: Offline Points: 12 |
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I replaced the prop with a one inch lower pitch, because most of what I do is idle or ski.
I haven't measured play for strut condition but the bearing looks good and shaft spins with ease. I will measure for out of round but I would think the vibration would increase, with RPM, if it is bent. The previous owner did stringer work and the mounts are now sitting on aluminum angle iron which I wonder about. Are new isolators readily available? Thanks, |
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68 Mustang Wes
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63 Skier
Grand Poobah Joined: October-06-2006 Location: Concord, NH Status: Offline Points: 4229 |
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I doubt isolation is the problem, or the fix. Since you mention the vibration is at it's worst when under max load, engine/prop loaded up trying to pull up a heavy skier, I'm going to guess you will find a worn out strut bearing. Could be wrong, but agree with above that it's strut or shaft or prop.
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dutch-us
Newbie Joined: August-19-2022 Location: Western Michiga Status: Offline Points: 12 |
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Thank you all and it's time to fire up the garage furnace and go to work.
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68 Mustang Wes
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