Vibration starts at 2000 rpm - SailNet Community
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post #1 of 9 Old 10-22-2013 Thread Starter
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Vibration starts at 2000 rpm

Hi All,

Still learning the new inboard diesel thing. I've read about boat/engine "harmonics"... From idle to 1980 rpm or so, you can set a glass of water on the cockpit table without a ripple. After 2000... it's vibration city (compaired to what it was before this crossover point). Where should I go to look for problems? Do I even have a problem? Not sure. The hull is clean and the 2 blade prop is clean and the Universal 5424 will achieve it's max rated 2800 rpm.

Dave

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post #2 of 9 Old 10-22-2013
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Re: Vibration starts at 2000 rpm

First, I would check the engine mounts and isolators to see if they are good condition

Second, check the cutlass bearing and strut (if applicable)

Third, check alignment of the shaft coupler. (.001 for every inch in diameter of the coupler ).

Fourth, I would call a mechanic
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Shawn

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post #3 of 9 Old 10-22-2013
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Re: Vibration starts at 2000 rpm

If you get the vibration when out of gear it may be something in/on the engine. If only when in gear, probably as T37 mentioned. Did it just happen all at once? If so, maybe you lost a shaft zinc or wound up some monofilament in your shaft/strut?

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post #4 of 9 Old 10-22-2013 Thread Starter
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Re: Vibration starts at 2000 rpm

The boat is new to us, so that's the way we got it. I do know when we hauled it for the survey, the cutlass bearing had just the tiniest amount of movement (to be changed later this winter when doing the bottom). Will look into the rest of it...thanks!

Dave

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post #5 of 9 Old 10-22-2013
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Re: Vibration starts at 2000 rpm

Good chance it is shaft alignment, vibration gets worse with RPM.

If it is motor mounts the engine will be moving a fair bit when idling, maybe a half inch or so.

If your cutlass bearing only has a little movement ( 1/8" ??) it is likely alright.
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post #6 of 9 Old 10-22-2013
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Re: Vibration starts at 2000 rpm

Definitely not normal. I have a 5424 and it smooths right out above 2000 rpm. Actually it's good above 1800. Although I have a 3 bladed prop.

Have you had a diver check the prop? A few barnacles can cause a lot of trouble.

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post #7 of 9 Old 10-23-2013
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Re: Vibration starts at 2000 rpm

We are not hearing whether this is occurring in gear or out of gear. It would be important to know to help diagnose.

Tod

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post #8 of 9 Old 10-23-2013 Thread Starter
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Re: Vibration starts at 2000 rpm

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Originally Posted by Gladrags1 View Post
We are not hearing whether this is occurring in gear or out of gear. It would be important to know to help diagnose.

Tod
I'll try that this weekend. The post is all about in gear, under way. I did watch the engine under way while the wife went through the RPM range and the engine was solid in it's mounts (no movement at all). Also, the cutlass bearing... MAYBE a 1/16th worth of play.

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post #9 of 9 Old 10-27-2013
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Re: Vibration starts at 2000 rpm

So far no one has mentioned a BENT shaft it is possible that a past owner has wound the dingy painter on the prop shaft It may be only at the taper and hard (imposible)to see It may only appear under a unique load .
I went through this from NY to Datona Beach finally had to pull the shaft to have it check The shaft looked fine except for a wear spot at the cutlass since it was off the boat I sent it out for a weld and machineeing to spec , I received a call that the shaft was (bent)by 1/1000 at the taper A new shaft later and all was go
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