88 OMC 460 King Cobra bad vibration...

cyclenut80

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Aug 17, 2009
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Ok this weekend I had the Four Winns Liberator out on the lake and all was well at first. The boat ran flawlessly for about 30 miles of lake shore thats when trouble started. I had the boat on plane at a nice cruise RPM, maybe 3-3500rpm. I noticed a slight vibration something like a plug wire maybe burning through. It felt like the boat was trying to drop a cylinder. I immediately throttled back and as soon as I did the engine and entire boat really shook quite violently. I shut the engine down and did a quick inspection. Everything looked good, wires in good shape and connected, no fluid leaks, no smoke. So I started it again and the engine vibrated pretty harshly even in neutral. As long as I had it running and figured it was already screwed up I pulled plug wires one by one to make sure I was firing on all eight cylinders. Of course this probably wasn't the best thing to do but you have to troubleshoot. The engine was running on all eight. This leads me to either the engine coupler or u-joints in the outdrive. These are the only parts that would be spinning in neutral that I can think of. I ended up limping the boat at basically an idle back to the dock. I did notice that if you pulled the throttle back while it was in gear the vibration smoothed out for a split second. All that tells me is that when the driveline is unloaded things seem better. Does anyone know of a way to check this without pulling the drive? I would just like to have an idea of whats wrong so when I make the repairs I can have all the parts I need handy. Thanks for all your help and feel free to move this to the Four Winns forum if need be.
 

danond

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Jun 11, 2007
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1,118
Re: 88 OMC 460 King Cobra bad vibration...

The drive takes 20 minutes to pull. Start with that.
 

cyclenut80

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Aug 17, 2009
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Re: 88 OMC 460 King Cobra bad vibration...

Yeah I pretty much figured I would need to pull the drive to be totally sure. Just really wanted to know if I was on the right track or if anyone had dealt with similar symptoms. I should have said that in my first post.
 

Bondo

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Re: 88 OMC 460 King Cobra bad vibration...

Does anyone know of a way to check this without pulling the drive? I would just like to have an idea of whats wrong so when I make the repairs I can have all the parts I need handy.

Ayuh,... The Problem is at/ in the Drive,.... That's where I'd start...

If you start Searching Now,... You might find most of the parts you'll need....
I hear the most common part # for the King Cobra outdrives is #NLA....
 

cyclenut80

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Aug 17, 2009
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Re: 88 OMC 460 King Cobra bad vibration...

LOL @ NLA...I hear you there! I got a super deal on this boat and it is in great shape but now I regret it after not listening to everyone about the Cobra drives, I just figured that the King Cobra might be a bit more reliable. I have had several MercCruiser drives on other boats and never had an issue. Oh well, live and learn. I have found all the parts I need...all but the engine coupler. I guess they are no longer available even in the aftermarket. If anyone knows where to find one let me know. I hear some people redrill the flywheel for a chevy pattern and use one from a 454 but I don't know if thats a real fix or not.
 
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