65 enclosed bridge vibrations

[stimmy]

I just joined on recommendation from a member of The Hull Truth, which I've also been a member of for many years. He felt I should ask the experts.
I am waiting to close on a Hatteras 65 with enclosed flybridge; everything was good until the seatrial. Boat survey good, engine survey (16V92's) good. During my seatrial, there was a fairly strong vibration that started at 1800 RPM that smoothed out at about 2000 RPM; I didn't detect it at any other RPM.
The boat surveyor didn't notice it a month ago during his survey.
The boat is over 20 years old and I'm not expecting a new boat, but I don't want to get into a huge unexpected expense before I can even use it.
It seems like out of balance wheel/s, bad cutlass/s, bad trans bearing/s, bent shaft/s, engine problems, even misalignment could be the cause. Where should I start first? I only have a limited time to accept or reject the boat.

 

[polarizer]

You've identified all the areas which could cause the issue.
I wouldn't close until the owner agrees to have the issue resolved.
As drive systems can effect other components within the drive system, including engine mounts, the seller should be willing to put an extension on the closing time.
The surveyor should be able to determine the status of the drive system. If the coupler needs to be unbolted, I would suggest doing so.

 

[Pascal]

Is the vibration noticed when decelerating from 2000 to 1900 then 1800 or only under accelerations. Could it be cavitation? Does the boat have underwater exhaust? sometimes the gases can get sucked in when accelerating.

A couple of months ago during a sea trial of a boat, the sportfish jock doing the driving just pushed the controls hard and quickly th boat started vibrating because of the exhaust casing cavitation. He Had to back down and get is right hand under control

 

[SeaEric]

How deep was the water where this occurred? On some larger boats, there can be unexplained vibration in water under about 20 feet deep.

 

[saltshaker]

As mentioned you hit the areas of concern. Is the vibration constant or only when accelerating? when you feel the vibration can you see and movement/vibration at the shaft or engine mounts? Do you feel the vibration at the bridge and down below? Mine does vibrate a bit at lower RPMs when the hull is working hard and not yet on plane but that's only in the 1400rpm range. It's more pronounced on the bridge and barely noticeable anywhere else. You should be running smooth at 1800RPMs. What kind of speed are you seeing at 1800, 2100 and WOT which should be 2300-2350? What props do you have?

 

[Pascal]

Eric, About 12'. I've put over 1500nm on th boat since early August and have learned to accelerate gradually to 1550/1600 at which the boat is on plane and doing 17/18kts. I does seem worst in shallow water. 8 to 9' is as shallow as I get on plane (5' draft)

 

[bobk]

Eric, About 12'. I've put over 1500nm on th boat since early August and have learned to accelerate gradually to 1550/1600 at which the boat is on plane and doing 17/18kts. I does seem worst in shallow water. 8 to 9' is as shallow as I get on plane (5' draft)

In my case, 12' is as shallow as I can easily get on plane. Deeper is better. And of course lighter is better. I think this is a bow wave phenomena.

Bobk

 

[Red Hatt]

I would not buy the boat until the owner made the vibration go away. You could spend at least $10,000 to make the repair. Trust me I know.

 

[saltshaker]

I would not buy the boat until the owner made the vibration go away. You could spend at least $10,000 to make the repair. Trust me I know.

That won't do much on a 65 if its anything significant. That boat has 4" shafts, big wheels very expensive gears etc.

 

[stimmy]

The vibration started when we accelerated to 1800 RPM and was constant there. I didn't go into the engine room during vibration since I didn't have hearing protection, but it was easily felt on the bridge. It didn't knock you around, but it was strong enough to be easily felt.
The water was about 30' deep in some of the areas where the vibration occurred. As the RPM increased above 1950 or decreased below 1800, it smoothed out with no noticeable vibration.
The engines both turned ony 2180 WOT, would not do the specified 2300, but the boat did hit 25.8 knots on the GPS. How problematic is that? It has the original wheels which are 38X40, 5 blade.
It's nice to be among experts who've been there. This will be the biggest boat I've owned.

 

[Tinman]

I would never close on a vibration issue, without the seller agreeing to fixing it. Sounds like you may also be over wheeled.

 

[saltshaker]

You've got a lot to go through. I would not accept the boat until I knew what was going on. The low RPMs are as much if not more of an issue than the vibration. 2180 is way too low. Speed is about right for 2180 but you should be running at least 2300 RPMs and 30kt or better. Was the bottom and running gear cleaned when you did the sea trial? Did you have an engine survey done or just the hull survey? How many hours on the boat? Any smoke on start up or while running? Post a link to the listing and hopefully we can offer some more detailed advice. The 65EB is an awesome boat but you don't want to start off needing repairs you are unaware of. Could be as simple as a bottom cleaning or engine tune but not something I would roll the dice with unless you're buying it cheap.

 

[stimmy]

Someone on the Hull Truth said to listen to Saltshaker so I'm all ears.<br>The boat reportedly has 2100 original hours. The boat and engine surveys were both good for a boat of that age. The engine surveyor noted the low RPM also. His report showed he scoped both engines with port cylinder walls showing no cross hatching, typical of 2100 hours. Neither engine smoked much on startup, but port smokes grey on acceleration. No noticeable smoke underway. He said starboard showed strong cross hatching indicating much lower hours, but the current owner (2nd) was unaware of a rebuild. He has donated the boat to a charity, from whom I will buy it.<br>The broker had a diver clean the bottom and props just before the sea trial; it made no difference from the surveyor's sea trial.<br>The boat is a bargain, as long as I'm not facing a $50K bill to get it running properly.<br>As soon as the hurricane is by (assuming the boat makes it through), I will tell them I will not proceed until the vibration issue is resolved.<br>My plan was to campaign the boat in tournaments for a few years. I was told the 16V92's will cost about $50K each to rebuild in place. Repower is prohibitive since I'd never get a reasonable return on them.
I can't post a link until I have more posts.

 

[stimmy]

I would never close on a vibration issue, without the seller agreeing to fixing it. Sounds like you may also be over wheeled.

I thought the same since it wouldn't reach 2300 RPM, but the boat has the original sized wheels. My thought then was that the engiines just can't make enough HP anymore.

 

[Pascal]

Short about 150 rpm is a pretty big issue, especially on a sportfish likely to have been run harder than a MY.

I'd talk to a reputable prop shop to see what they think of a vibration that shows up only in a narrow range. If a wheel was bad I woudl think it woudl get worst at higher rpm.

Making sure the shafts are true isn't too hard but needs to be done on the hard.

$50k to rebuild one of these sounds very cheap... Again, talk to a good Detroit shop to get a better idea of the cost as the la k of cross hatch on one of them isn't a good sign either.

 

[Finalee]

The last 30 days in a lot of areas was the peak barnacle growth season. Agreed that you are taking a big risk not knowing what it is. Possibly could be growth on the running gear. Start with the easy stuff first. Growth could cause the low rpm as well.

 

[stimmy]

Short about 150 rpm is a pretty big issue, especially on a sportfish likely to have been run harder than a MY.

I'd talk to a reputable prop shop to see what they think of a vibration that shows up only in a narrow range. If a wheel was bad I would think it would get worst at higher rpm.

Making sure the shafts are true isn't too hard but needs to be done on the hard.

$50k to rebuild one of these sounds very cheap... Again, talk to a good Detroit shop to get a better idea of the cost as the la k of cross hatch on one of them isn't a good sign either.

Thanks, but it may be academic; boat is in Stuart, tied to a dock. Owners couldn't get it pulled; it may not exist tomorrow.
It was a Detroit shop that said $48 to $52K for a complete rebuild, depending on if it needs a crank, etc. to be replaced. I can't see how they can rebuild those big beasts in place.

 

[stimmy]

link to boat ad:
http://www.uyslist.com/yachts/2714/brochure.pdf

 

[madhatter1]

stimmy, good to see you made it to the right place to get some info.

If it all works out maybe I could get a ride. Never been on a beast like that.

Good luck.

 

[Tinman]

I thought the same since it wouldn't reach 2300 RPM, but the boat has the original sized wheels. My thought then was that the engiines just can't make enough HP anymore.

Could be, a lot of sportfish boats have had pitch added to the props to get a couple of knots speed. Saltshaker is definitely the go to on the 65c. The pics look good. Hopefully it will be ok after Matthew, good luck.