Boat vibration at low speed

Here's how to diagnose and remedy common propeller problems1. I am currently running ACE mounts and was wondering if changing the mounts out to Barry Controls or Isoflex would be beneficial. Another is to provide reverse rotation so that you can back your boat into your slip. The faster you try to go, the worse the vibration is. Your boat dealer or boat builder should be contacted.

I had the prob balenced and straightened and the problem went away. You might also notice the engine racing, while the boat loses speed. My prop is in pretty bad shape could this be why? Jump to content. Now this only happens when you are slowing down and when you hit 25mph is when you feel it. It seems to start easier too, especially warm start. Low-Speed Main Diesel Engine For a very long time, this has been known to be the number one cause for vibrations in the hull girder. Since all buffers have what is known as a soft start and can be set to very low operating speeds, any beginner can start slowly and work your way forward.

This guide is designed to help you track down and hopefully correct any problems in that arena. As the engine speed increases, the vibration ceases - because the driving frequency increases to that above the natural frequency of the boat and components.

Bent or broken shafts ; Drive system vibration that can damage transmissions, engine mounts and the boat hull itself. With a custom HO Bostrom seat, you may combine components to meet your special needs; i. It runs great but when it is barely in gear it has alot of vibration. I have checked it all over when the boat was on the slip, but found no obvious reasons.

We hit the sand-bar at low speeds probably in the mph range and didnt't think a whole lot about it until this season when we took the boat back out and noticed the vibration. Learn how to track down inboard engine vibrations so they don't rattle your soul. Monitoring shaft speed is a fundamental aspect of hazard monitoring and should be utilized by any facility with rotating shafts. Vibrations at high speeds can lead to tire failure and serious accidents.

The transom must be sufficiently strong when mounting more than an inch above the original transom top.

boat vibration at low speed

Doesn't sound like it is laboring. The boat Grady noticeably shudders at that speed.

Reasons for vibration in boat?

InI took my car to a mechanic where he diagnosed the problem to be the center bearing. Three periodic forces and periodic moments acting on the engine govern the excitation of the diesel engine. It is that slight. Vibra-Stop cures outboard motor vibration. You know you never hit bottom, but suddenly hatch hinges clatter while underway, and a tingle starts in your feet and travels all the way through your spine.

The boat can be divided into three categories - jet unit, engine, and hull. Sounds kind of like a slow-speed misfire under load. I have noticed this on my boat and others as well. My mechanic verified the alignment and said it was spot on. Since it goes away at high speed I guess its not a balance issue. Set a low buffer speed for better control.

An unexpected change in the performance of your boat motor can put a damper on a day of fun on the water or even prevent you from leaving the dock. Boat Engine Troubleshooting. Any suggestions on what the issue could be is greatly appreciated.Any content, information, or advice found on social media platforms and the wider Internet, including forums such as YBW, should NOT be acted upon unless checked against a reliable, authoritative source, and re-checked, particularly where personal health and liberty is at stake.

It is your responsibility to provide references to bona fide sources. Forums New posts Search forums. What's new New posts Latest activity. Log in Register. Search titles only. Search Advanced search…. New posts. Search forums. Log in. JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding. Reasons for vibration in boat? Thread starter mikef Start date 27 Aug I've had a vibration in my boat which has got steadily worse as the season has gone on.

It's mainly apparent at slow speed and seems to disappear at high speed. As far as I'm aware I haven't dinged a prop and visually, I can see no damage to the props or any other sterngear bits.

boat vibration at low speed

The drive system on my boat is a simple shaftdrive system with engine, gearbox and propshaft in line; there is no universal coupling or down angle gearbox in the drive system. Could it be that one or both engines have settled on their mountings causing the propshaft to become non-concentric in the stern tube?

How do I check for that? Are there are other possible reasons? BartW Well-known member. Joined 9 Oct Messages 4, Location Belgium. If it seems to disappear at high rpm then I would think that clears the shaft line etc as a failed bearing or misalignment would likely get more noisy at higher rpm.

It could be an engine vibration which in which case as the rpm went up the vibration frequency harmonises thus reducing what you hear.

How to Diagnose and Fix Inboard Shaft Vibration

This could be transmitted to the boat via a hardened mount etc and what you hear is actually likely to be another part of the boat such as cabinetry etc being vibrated. If it just appeared this season it is likely that its due to something wearing out which will only get worse. Of course all of this is guess work as I'm not there and can't hear it. Joined 14 Mar Messages 8, Location London. Joined 10 Oct Messages 5, Location west yorkshire. Portofino Well-known member.

Hi, Work out which engine it is. First I would check the prop ,have you cleaned it evenly? If its dinged these nowt you can do until lift out. What state is the shaft anode -missing a bolt or eroded unevenly? Does it come on in neutral or with spinning props? Have you got a spanner big enough? Gearbox -oil level or any way of checking using a inferred thermometer if one is hotter than t,other ie wearing out prematurely?. Hope not.As an outboard or stem drive is progressively raised, the propeller will eventually break the surface of the water.

When Im coming into my slip there is a disturbing thumping with in neutral and at idle that also goes away around rpm. Shown is the model VSST backing pad. When driving the boat I just avoid that speed range but since I have a significant no-wake area it would be great use it.

If something is "wrong" with the boat it is usually poor acceleration and load carrying, coupled with excessive fuel consumption or engine RPM's. Maybe we need to fair the rudder. Selecting the right propeller Boating Magazine Fpchief: Not to say this is the reason for your vibration, but as Rickdb1 said, it could be the nature of your beast. If you notice any erosion, replace the plug.

The only trend is that the vibration generally increases with speed. Simply lower the rpms to the lowest setting to obtain the low speed needle valve adjustment. We hit the sand-bar at low speeds probably in the mph range and didnt't think a whole lot about it until this season when we took the boat back out and noticed the vibration.

The testing showed the Sharrow put the boat on plane quicker, was faster at all RPM settings, was more fuel efficient at all RPM settings, produced the highest top speed, and significantly cut We hit the sand-bar at low speeds probably in the mph range and didnt't think a whole lot about it until this season when we took the boat back out and noticed the vibration.

Choose a range of propellers to perform a water test.

Bad Vibrations

Low-Speed Main Diesel Engine For a very long time, this has been known to be the number one cause for vibrations in the hull girder. Went from 17 to 15 pitch prop. The largest bass fishing site on the Web! I own a Speedster with 85hp twin Rotax. You might also notice the engine racing, while the boat loses speed. As the engine speed increases, the vibration ceases - because the driving frequency increases to that above the natural frequency of the boat and components.

Preventing prop ventilation with crew seated forward 2. Vibration-dampening gear that will help keep you from feeling worn out after a day on the water. It runs great but when it is barely in gear it has alot of vibration.

One is to engage and disengage the engine from the propeller—in other words, to provide neutral. Most of them are felt in the steering wheel and can be traced to the front end of the car. I had a mechanic inspect and change lube in the lower unit he gave it the thumbs up without actually see or here it run.

Could thereStill learning this inboard stuff. Set the trim angle so the boat has optimum speed on top of the water. Remove all your spark plugs with a ratchet and appropriately sized socket.

Since all buffers have what is known as a soft start and can be set to very low operating speeds, any beginner can start slowly and work your way forward. Shakes everything in the boat I guess it's time for a road trip to see Ricky the prop guy in Brainerd and see if he can help me out. If it's a carbed motor, I would think a slow-speed mixture needle maybe needs tweaking. Tried it in my driveway tonight and same thing, with boat in gear low rpm alot of vibration, high rpm almost none.

The bubbles stick to surfaces and essentially increase the thickness of prop blades and more power is needed to increase or maintain speed. I had the prob balenced and straightened and the problem went away. Now I have ocassionally run the prop into a barely submerged sandbar and even hit a log the trip before, but these were all relativly soft and resulted in little more then some paint loss and some very shallow gouges in the edges.

Any suggestions on what the issue could be is greatly appreciated. If left unchecked, it could be doing significant damage to your boat. I am currently running ACE mounts and was wondering if changing the mounts out to Barry Controls or Isoflex would be beneficial.

Boat Engine Troubleshooting. Test the props under the same conditions that you would typically use the boat—same load, gear, and water.Unwanted vibrations could be more than annoying; they could be doing some real damage to your boat. Here's how to identify and fix those pesky percussions. Illustration: Mark Franklin Arts. Vibrations may be good when listening to rock and roll, but unless you have the stereo pumping, anything causing vibrations is often indicative of an issue with a component on the boat.

Unwanted vibration is more than just a nuisance. If left unchecked, it could be doing significant damage to your boat. Often, the source of onboard vibration can be traced to problems with the engine and running gear. This guide is designed to help you track down and hopefully correct any problems in that arena. Because the parts in the drive train and running gear are interconnected, something that is worn or out of alignment puts extra stress on other components that may also suffer.

All boats vibrate to some extent when they're underway, and over time, you, the owner, will become attuned to your particular boat's characteristics. But if you become aware of something new, or it just does not feel or sound right, then it may be time to carry out some investigative work to find the culprit.

Some vibrations emanating from something like an excessively worn engine mount, for instance, may produce a distinctive metallic sound, helping you home in on the problem. On the other hand, many vibrations have no distinctive or easy-to-source sounds, and although they may be felt, you can't hear them, making tracking down issues harder. Steve Zimmerman, President of Zimmerman Marine, who runs four repair yards in Virginia, Maryland, and North Carolina, says that tracking down unwanted vibrations can be tricky.

Look for worn areas under bearings and around the stuffing box. On some boats where there is a large section of the shaft visible, it may actually be possible to spot a bent shaft. Watch closely from different angles while you get a helper to turn the shaft slowly by hand. When the boat isn't running, you can run your finger around the shaft where it enters the stuffing box and see if you can feel any wear, which could indicate an excessively worn shaft, a potential cause of shake and vibration.

When it is hauled, damage to props is often easier to spot with the naked eye; look for dings, dents and gouges, even something seemingly inconsequential can throw things out of balance and cause vibration when the prop is rotating at high speed.

You can do a basic check to make sure the blades are even by measuring the distance from each blade tip to the same spot on the hull or a block of wood placed directly under the boat. In this guide, we are going to concentrate on inboard engines.

That's not to say that outboards don't vibrate, because they do, but these are outside the scope of this article. Inboard engines have a lot of things attached to them, such as transmissions, reduction gears, propshafts, and propellers, all of which can be the cause of undue vibrations. For this article, we are assuming there is only one engine. If you have twins, then it's often helpful to check one at a time. Sometimes having a pair of engines can be beneficial as it's possible to check one against the other.

If one is noticeably different in operation to the other, then you'll want to find out why. What follows is not a comprehensive guide by any stretch, but it will, hopefully, help you identify the source of any unwanted vibration, starting with the simplest causes. Once you've found the reason for the annoyance, you can do something about getting it fixed. And although you may not be in a position to carry out repairs yourself, your yard or mechanic will thank you if you can accurately describe and narrow down the source of any problems.

Inspect each engine mount in turn. Is one shaking more than the others? Is there excessive rusting or rubber residue adjacent top one or more of the mounts? A rough-running engine can lead to excessive vibration. Run diagnostic checks in accordance with engine manufacturer's recommendations.

Remedy: Have the propeller lapped to the shaft to fit the taper correctly. Lap prop taper to ensure it fits correctly. Install new key. Check prop with a dial gauge to ensure it is in round.Vibrations can come from OK causes, but usually they come from problems ranging from small to huge to potentially catastrophic. Here are a few. Those of you who remember the song "Good Vibrations" by the Beach Boys may have some warm and fuzzies.

But with boats it's different.

boat vibration at low speed

Most vibrations are bad We've had a lot of Ask the Experts questions about vibrations. Almost all of them have been from boaters who felt that something wasn't right and who have tried to figure it out and fix it. This is a very good thing. Often these boaters saved a lot of money and hassle by simply paying attention to what the boat was telling them.

A cutlass bearing resides in the strut. The shaft passes through it. You may have a second one residing in the outside of the shaft log where the shaft passes through the hull. Their purpose is to prevent the shaft from wearing and abrading on damaging material such as fiberglass or bronze and to help it to turn true and with support. But this bearing is sacrificial.

Usually it is a rubber or synthetic material that's encased in a bronze housing that's inserted into the strut. The shaft turns in this and the "rubber" is, of course, softer than the shaft. Grooves run up and down the "rubber" to allow water to wash through to help with lubrication and cooling. But these wear with time and then the shaft has play within the cutlass bearing. It can cause excessive leaking at the packing gland, damage to the transmission and other things.

Often you first notice this by a vibration. It's fairly easy to confirm the problem. When the boat's hauled you ask a knowledgeable yard worker to grip the shaft and try to move it in the bearing. An experienced diver can also check this. If the yard has the right tools and ask if it has a cutlass bearing puller this isn't a big deal to replace.

If you don't fix this, it can be a very big deal. Another vibration can come from a bent or worn shaft. If you've experienced a grounding and who hasn't there may be some impact to your shaft and it may be out of true.Forums New posts Search forums.

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boat vibration at low speed

Log in Register. Search titles only. Search Advanced search…. New posts. Search forums. Log in. For a better experience, please enable JavaScript in your browser before proceeding. Vibration at low speed. Thread starter cortez Start date Jun 24, Joined Mar 29, Messages My drive or engine has a vibration at between to rpm,I have tried the trim in and out also with and without tabs.

At higher revs there is no problem at all,my engine is a volvo 5. I do have a small ding in one prop,could this be the prob or should I be looking elsewhere. Good Sport Cadet. Joined Jun 8, Messages Re: Vibration at low speed Sounds like your prop to me. It's probably bent in addition to dinged. Don S Honorary Moderator Emeritus. Joined Aug 31, Messages 62, Re: Vibration at low speed The prop could be your vibration, while a small ding may not cause it, I had a customer who also stated he had a small ding and a vibration.

Turns out his small ding was smaller than half a dime, it also had the tip of the blade bent over. New prop cured his problem. You could also have bad ujoints, bent prop shaft, or for that matter, just a rough running engine, possibly a dead cylinder. Joined Jun 6, Messages I hadn't hit anything, so I thought I might have picked up a piece of rope, ect.

I dove in and checked it and found the whale fin on the outdrive had come looseNext time you find yourself floating chest deep in water, try this little demonstration of cavitation in action while you are waiting for everyone to stop laughing and pull you out of the water.

Hold the palm of your hand vertically and pass it quickly back and forth through the water. You will see a stream of bubbles form opposite the direction of travel. These bubbles are what is called cavitation. In the case of boats and ships, cavitation refers to a pocket, or cavity, of air forming on the backside of a prop or impeller blade.

The most simple definition of cavitation is; an action that causes a void to form because of lower pressure. As the definition above says, the condition of cavitation is caused by a low-pressure situation.

When you moved your hand back and forth through the water you caused the pressure behind your hand to drop. That's where the bubbles formed. A prop with too much pitch or too much shaft speed will cause pockets to form on the back side of the blades or even at the tips. The reason these voids form is boiling of the liquid. This is not boiling from heat, but boiling from the vacuum. Physics experts tell us that a liquid will boil if heated to a certain temperature or if the pressure of the liquid is reduced.

In the case of cavitation, the reason is lower pressure. This cold boiling technique is good for many industrial uses, but it is not wanted near props or pump impellers. The collapsing bubbles are filled with very low-pressure water vapor and when they collapse damage is done to many surfaces. Cavitation is a drag on efficiency because of the increased friction.

The bubbles stick to surfaces and essentially increase the thickness of prop blades and more power is needed to increase or maintain speed. Even worse, cavitation can cause vibration because of uneven prop loads and damage or break equipment. Even worse than vibration damage is pitting. Pitting happens when bubbles collapse and all forces are focused on a tiny spot on the blade surface.

Damage from vibration is very noticeable and usually preventable with modifications to operating style. Damage from pitting can be happening at a very subtle level and most of the affected components are out of sight in day-to-day operations.

An increase in power caused by a poorly adjusted governor can be enough to start minor cavitation near the prop tips and probably would not be noticed by most crews.

Only at haul out would the damage to drive components to be noticed. Pitting increases surface area which causes corrosion and few anti-fouling coatings can withstand forces from collapsing bubbles that can eat into hardened steel.

This same set of conditions and the resulting damage can also happen inside things like pump housings and thruster tunnels. Cavitation is actually much easier to produce in an enclosed environment than in an open situation like a prop and shaft. In an enclosed area, there is much less liquid volume to rush in and compress the vacuum bubbles that are forming. Cavitation inside pumps is a leading cause of failure.

Turning a centrifugal pump too quickly causes the liquid in a pump chamber to boil from lack of pressure. This is even more of a problem if you are pumping a hot liquid like coolant or heavy fuel oil.

How an outboard gearbox works

In a hot liquid situation, you are applying two sources of energy that will make the liquid boil. The first, heat, is external and is the better-understood form of boiling. The second is the mechanical vacuum caused by the impeller. Share Flipboard Email.


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