Vibration

[micky]

I had the stbd. engine out of alignment. and aligned it 2 weeks ago. Last weekend I had the boat out and there's no vibration up to 1800 rpm. From 1800 up it vibrates like crazy. My dad told me that if it is a bent shaft it will vibrate at any rpm so that it must be the cutlass bearing. I went underwater and turned the prop by hand and the stbd. prop is harder to turn by hand than the port.

What do you guys think? Thanks.

 

[rwetherington]

what model yacht and what engines when where the props last balanced?

 

[saltshaker]

How far out of alignment and in which direction? What was the change after the alignment? Is the shaft centered at the shaft log? What type of engine mounts and what condition? It very well may be a cutlass bearing but you need to check everything else too. I don't think there's a good way to check the cutlass bearing in the water unless you have excellent visibility. You also need to check the shaft/strut alignment. If you've been running for a long time with the engine out, everything else may need to be adjusted.

 

[micky]

Its a 1974 43DC with 671n Detroit engines. The engine was about 1/2" higher than the shaft. I lowered the engine for a perfect match. The props were balanced about 8-10 month ago, in that period of time I used the boat 2-3 times because of the overheating issue I had with the heat exchanger, I could not go over 1100 rpm. The day we replaced the heat exchanger we took it out for a sea trial and when going over 1800 rpm it started vibrating like crazy. Weekend after that I took the bolts out of the coupling and trans. and the engine was higher than the shaft. so I lowered the engine for a perfect match. This past weekend I went for another sea trial and it started vibrating after 1800 rpm. When I got to the beach I went into the water and the non vibrating engine I could rotate the prop without any restriction. The vibrating engine I had to use a little force to rotate it by hand.

 

[capttonyf]

If everything is aligned and straight while at rest, and boat runs smooth up to 1800 and then begins to vibrate your problem my be somthing somewhere is loose, "not tightend fully". So at rest and up to a certain amount of torque being placed on your hull and drive system everything is ok, but once that extra amount of power/torque exceeds whatever is loose, ability to stay aligned it begins to vibrate. What looks aligned at rest and up to 1800 may change and go out of alignment above that RPM/Power and torque load. I ran a early 90's 63 Ocean Yachts for Mechanical/Vibration Sea trials. And took us about 5 before we figured out what was happening. At the Dock and at Moderate Speeds "RPM" the boat was Vibration Free perfectly aligned and ran great. But once we began to push it to higher speeds and RPM she bagan to vibrate like crazy, almost like it was out of alignment. We came back to the barn, checked it out and agian it was perfect. We were stumped. Everything was tight and checked out fine then someone suggested we tie a string with a sinker on it TIGHT between the engines and run it again. Up to about 1500 it was tight, 1600 it bagan to dip a little, 1800 a little more but not to bad until we really bagan to push it and the string developed a bigger dip, loosened up and the boat began to vibrate again. It was determined that the hull under heavy load was flexing and throwing out the alignment. Not sure how they eventually eliminated the flex but they did. I'm not saying your Hatteras hull is Fexing like this Ocean Yachts did, but Under Heavy load something assuming Wheels are good is moving, a strut, motor mount or even an old weak shaft that maybe over flexing under the heavy load. Point is what maybe straight at the dock may not be under heavy load, real world conditions at sea.

 

[saltshaker]

Take a good look at the motor mounts and see if they are sagging.

 

[doc g]

If the motor mounts were sagging wouldn't the engine have been too low for the shaft when it was uncoupled to check the alignment ? Just wondering ????....Pat

 

[capttonyf]

Im NOT a Mechanic but just thinking, you mentioned you lowered the engine 1/2 inch then after a while you moved it again. Keep in mind just because you lowered the engine to match up the with the shaft dos NOT mean it's in align with the shaft. I would think to keep alignment if you lower the rear of the engine you would more than likely have to Raise the Front. if not, I would think its off alignment because you altered the agle of the motoe from the angle of the shaft. The rear height maybe correct but Not the alignment. Again I'm by no means a mechanic, just thinking.

 

[Bill Allen]

With my 43 when you pull the coupler apart you'll get some sagging of the shaft. But you lift it up slightly and in this case use a feeler gauge to gap the coupling all the way around. raising it what you raised it are you pulling our legs? Far as flexing in the hull, again are you kidding me? The 43's like all the old hatt's are friggin tanks overbuilt at the very least. It sounds to me like something really out of wack it sounds as if you may have moved the engine too far and still don't have the alligmnet close. Checking mounts, good idea, checking props, good idea, But I'd lean at mounts and shaft alligment Bill

 

[Maynard Rupp]

The important issue with alignment is the mating of the 2 flanges, not whether the shaft and engine might not meet each other when uncoupled. You need to mate the two flanges, put one bolt and nut in, then use a feeler gage to see that the two flanges are the same distance apart all around the OD of the coupler flanges. That's what alignment is.

 

[capttonyf]

With my 43 when you pull the coupler apart you'll get some sagging of the shaft. But you lift it up slightly and in this case use a feeler gauge to gap the coupling all the way around. raising it what you raised it are you pulling our legs? Far as flexing in the hull, again are you kidding me? The 43's like all the old hatt's are friggin tanks overbuilt at the very least. It sounds to me like something really out of wack it sounds as if you may have moved the engine too far and still don't have the alligmnet close. Checking mounts, good idea, checking props, good idea, But I'd lean at mounts and shaft alligment Bill

I didn't say the Hatteras Hull was flexing I actually stated the opposite "I'm not saying your Hatteras hull is Fexing like this Ocean Yachts" I was using it as an example that just because it's OK at rest doesn't mean it's OK under Power. There could be somthing else moving wihile under power, such as a Strut, Mount, or even an old weak Shaft that when spun at high RPM under a lot of torque, begins wobble. Even a semi loose rudder would cause vibration although it would be more of a chattering vibration and you would probably see water entering. Notice I stated I'm not a mechanic, just young salty, and it is very tough to determine anything without seeing it. I'm only offering idea's and possible things to check from my expierience.

 

[Bill Allen]

Don't get your underwear in a bunch. Struts as I rememeber two on a side if they moved should see water leaking into the hull. Got better when he moved the engine, BUt a 1/2" that's a lot, but it got better so mounts and aligment. Need to first check the mounts, realign the coupling then check it out. Would have said a prop but it got better when he moved the engine. Look for metal/ rubber debris around the mounts maybe even shiny metal around them. Also put a wrench on both the mount and the bolts that hold them to the stringers make sure everything's tight and not moving around. My mounts look like hell but when we changed the pan turns out they were fine. If the engines moving around you'll probably see something shiny or at least an area thats not quite normal. In the old tiny engine room 43's you need a good light and maybe a mirror to see around the mounts. Check everything out, twice, reallign the coupling and take it out. Mine also vibrated when I had an injector issue but since it changed when you moved the engine guess thats the way to go. Bill

 

[capttonyf]

Don't get your underwear in a bunch. Struts as I rememeber two on a side if they moved should see water leaking into the hull. Got better when he moved the engine, BUt a 1/2" that's a lot, but it got better so mounts and aligment. Need to first check the mounts, realign the coupling then check it out. Would have said a prop but it got better when he moved the engine. Look for metal/ rubber debris around the mounts maybe even shiny metal around them. Also put a wrench on both the mount and the bolts that hold them to the stringers make sure everything's tight and not moving around. My mounts look like hell but when we changed the pan turns out they were fine. If the engines moving around you'll probably see something shiny or at least an area thats not quite normal. In the old tiny engine room 43's you need a good light and maybe a mirror to see around the mounts. Check everything out, twice, reallign the coupling and take it out. Mine also vibrated when I had an injector issue but since it changed when you moved the engine guess thats the way to go. Bill

"Don't get your underware in a bunch". I wasn't, I agree with you, I actually think most og these old boats are over built and I know would never flex. That's why I own one. I would rather have a little slower over built, solid feeling boat than what most of whats being built today. I'm a believer in over built.

 

[capttonyf]

"Don't get your underware in a bunch". I wasn't, I agree with you, I actually think most og these old boats are over built and I know would never flex. That's why I own one. I would rather have a little slower over built, solid feeling boat than what most of whats being built today. I'm a believer in over built.

It's actually funny, yet unfortunate when people get upset and their feeling hurt on sites like this,, I don't understand it.

 

[Bill Allen]

There's no doubt they're overbuilt and strong. They'll take way more then the people inside of them. I really enjoy my old hatt, but then I'm old and overbuilt as well, actually maybe just old and a tad fat.Bill

 

[capttonyf]

There's no doubt they're overbuilt and strong. They'll take way more then the people inside of them. I really enjoy my old hatt, but then I'm old and overbuilt as well, actually maybe just old and a tad fat.Bill

"tad fat" Noooo, Just tell people, yesterday I was skinny until that Bee Stung me.

 

[jim rosenthal]

What might be helpful is for someone to actually be in the engine room while this is happening.

I am not volunteering, you understand. I, myself, am too old and too fat as well. Some of us here are gaining in girth what we have lost in hair.

 

[capttonyf]

What might be helpful is for someone to actually be in the engine room while this is happening.

I am not volunteering, you understand. I, myself, am too old and too fat as well. Some of us here are gaining in girth what we have lost in hair.

Some men are too concerned with balding, me personally I'm going down gracefully, once it's gone it's gone. I keep high and tight anyway. It doesn't matter, I"ve had women ask me for a lot of different things in my life time and not once has any of them asked for MORE Hair,,, Money maybe, But Not Hair.

 

[jim rosenthal]

I quit fighting it a long time ago. Haircuts have gotten cheaper as well. Only downside is if I don't wear a hat, my head burns. Painful.

 

[dsharp]

Have you tried standing on the back deck over each strut while someone runs the boat and see if you can tell which side is vibrating. I worn strut won't usually cause much vibration. Once you put it in gear the shaft loads the top of the bearing anyway. Look at each shaft underway and see if is oscillating or whipping the stuffing box up and down.the tight turning could just be from packing unless you recently hit something. It's not normal to have to drop the back of the engine 1/2". As stated the shaft will usually drop a little when it rolls out of the reduction gear coupling. The old style detroit motor mounts were bad about shearing the rubber and letting the mount drop.