Crankshaft Pulley Wobbles: Why and Does It Need to Be Fixed?

Crankshaft Pulley Wobbles: Why and Does It Need to Be Fixed?

If you are boating in deep fresh water and all of a sudden experience vibrations in your boat that are caused by the crankshaft pulley wobbling, you should be concerned about both your boat and engine.

It is not necessary for you to be concerned since the issue that will be covered today is the reason why the crankshaft pulley shakes and whether or not it needs to be fixed.

As a side note, the wobbling of the crankshaft can be caused by a number of different variables, each of which I will go into further detail about in a later section. Nevertheless, I am certain of one thing, and that is the fact that you should get it fixed as soon as you become aware that it is wobbling.

Before beginning the investigation into the causes of the wobbling, it is critical to acquire knowledge concerning the significance of the crankshaft pulley as well as the functions it performs.

What is a Crankshaft Pulley?

The alternator and a number of other components of the engine are driven by a pulley that is attached to the crankshaft. This component, which can also be referred to as the harmonic balancer, can be found near the very front of the crankshaft. In addition to this, the wheel that appears to be positioned on the crankshaft is in fact the pulley.

The crankshaft is responsible for generating rotational energy, which is then transferred to the crank pulley and used to power other components of the vehicle. In order to prevent the belt from sliding throughout the rotations, it has ribbing on it.

One of the primary functions of the crankshaft pulley is to dampen vibrations that are transmitted through the engine.

Its primary function is to rotate the belts that control the engine and the other components. In addition, it has storage for two distinct belts, or maybe one serpentine belt, that run the air conditioner and alternator. The year, as well as the kind of boat, determine whether a single strap or a whole system of belts is necessary.

For example, up until the middle of the 1980s, the majority of boats used V-belts to drive the various components of the engine.

You must be wondering about the belt-driven features and components. These include coolant circulation, providing charging for the electrical system, and hydraulic pressure. Other optional accessories include an air conditioning compressor and heavy hydraulic pumps.

Causes of Crankshaft Pulley Wobbling

The unfortunate news is that there is a chance that the pulley could develop a defect over the course of time and would need to be replaced as a result.

It is simple to check for the signs that indicate a problem with the crankshaft pulley. There is no question that one of them is swaying. However, if the crankshaft pulley is broken, the engine will make a loud banging noise and the other components of the engine will not function properly.

Some other symptoms to check are:

  • Abnormal engine vibrations
  • Alternator failure
  • Power steering pump failure
  • Transmission damage
  • Irregular idle engine speed

Rubber Belt Condition

In addition to that, you have the option to inspect the state of the rubber belt. It is possible that timing issues could arise and that it will wobble if it is broken or worn out.

Another possible explanation is that the bolt on the crankshaft that holds the pulley to the engineer has become loose. You do not need to replace the belt if it becomes loose at any point. Instead of investing money in purchasing a new belt, you may save money by simply tightening the bolt.

Crank Bolts Not Tight Enough

Moreover, if the crank bolts aren’t tight enough, the bolt starts to lessen and subsequently causes the crankshaft pulley to wobble. Not only that, it chews up the crank keyway and woodruff key.

Failure in Any of the Two-Part Assembly

The pulley that is attached to the crankshaft is made up of two pieces that are separated by a flexible layer. While the exterior assembly is made of hefty metal, the center component is fastened with bolts to the crank. In addition to this, the rotating mass helps to smooth out the pulses caused by the engine firing.

On the other hand, if any of the two components fail, it is imperative that they be replaced right away.

No Wobbling Effect at High RPM

Sometimes the crankshaft pulley will shake, but if the engine speed is high enough, you won’t be able to hear or feel any squeaking. Do not overlook such a scenario, since this is the sincerest advice I can provide you.

The reason for this is that the pulley has a center breakage, which, at higher RPMs, is virtually undetectable. If you choose to disregard it, it might end up causing some significant harm to the engine itself.

Poorly Manufactured Pulley

It’s another common reason which causes the crankshaft to wobble.

If the input rate of rotation is greater than the rotation’s output rate, it’s known as underdrive. A poorly designed pulley can face serious side effects due to underdrive in the power steering, air conditioning units, or alternator.

Belt length

Sometimes, the belt isn’t of the right length or the number of grooves. For instance, you may be using a five-groove belt to a six-groove pulley or vice versa.

Consequently, it may lead to the wobbling of the crankshaft pulley.


If you are involved in an accident that directly hits the crankshaft pulley and causes damage to it, you may experience wobbling as a result.

Distorted Fan-Belt Pulleys

It is possible for the crankshaft pulley to wobble if the fan-belt pulleys that bolt to the harmonic balancer are dismounted, deformed, or otherwise damaged. Dismounting the pulleys might also cause wobbling.

The typical tools may be used to remove these pulleys from the system. After that, inspect them for any signs of corrosion or flatness. It’s possible that some dirt will become lodged under the pulley at times.

In addition to this, if the crankshaft pulley is not torqued adequately, it has a tendency to wobble.

Over Tighten Drive Belt

The crankshaft pulley can be damaged if the drive belt has been tightened too much, which can also result in a severe imbalance.

Normal Aging

A crankshaft pulley comprises many parts, including inner steel, rubber isolator, and outer steel. Aging is a natural process that can cause contamination or defects in any of the layers.

The only feasible solution is to replace the pulley.

Effects of Crankshaft Pulley Wobbling

The crankshaft is made of heavy-duty cast iron or solid steel. That’s why it’s strong enough to withstand the stress of placing the crankshaft pulley. Furthermore, the tension increases from driving all the components off the single pulley.

If the crankshaft pulley starts to wobble, it will eventually throw off the belt. Not only that, but other components that depend on the pulley’s drive power will ultimately fail.

Fixing Crankshaft Pulley Wobbling

To your good fortune, the fasteners and other thread-locking substances that come standard from the manufacturer can be used as a fail-safe method to tighten the crankshaft pulley. In addition to this, the pulley stays in its position for a significantly longer amount of time.

Check the bolts

A round-shaped pulley is usually attached to the crankshaft by a large bolt and a thick washer at the center. Else, four small bolts around the inside edge of the pulley hold the shaft. Both these scenarios depend upon the vehicle model.

All you need to do is to remove all the belts which are driven by the crankshaft pulley. Later on, you can see if there are any loose bolts. It’s better to tighten all the bolts to be sure.

Furthermore, remove the large bolt using a strap wrench to check the damages on the crankshaft itself.  In case the end of the crankshaft is damaged, you are only left with one option – replace the crankshaft.

Internal Dampener

Many crankshaft pulleys come with an internal dampener, which ultimately reduces the vibrations running along with the pulley belts. In this way, you can save the connected system from any kind of potential harm.

By the way, you can individually replace a broken or worn-out crankshaft pulley belt. On the other hand, if a dampener becomes faulty, you’ll have to replace the entire crankshaft pulley.

Remove Dirt

You can remove the belt to ensure there isn’t any dirt, grease, sand, or belt material jammed in any of the grooves. Additionally, check the smooth-sided pulley for damage, dent, or dirt.

How to Replace a Crankshaft Pulley?

You can easily obtain an engine pulley remover on rent from an auto parts shop. All you need to do is to unscrew the central bolt and remove the defective pulley from the engine.

Moreover, you can follow these steps to fix/replace the pulley:

  • Disconnect the battery
  • Remove the drive belt
  • Remove the old pulley
  • Install the new pulley
  • Finally, torque the pulley

You can easily get a GEARWRENCH Pulley Puller and Installer Set, including one puller, one jackscrew, one bearing, one thrust washer, puller ponds, and four screws. GEARWRENCH is a reliable company renowned for its reliable automobile products and kits.

However, if you don’t want to buy a professional kit, you can simply opt for an Opall Crank Pulley Tool Kit. It comes with a crank pulley tool, one reinforcement ring, and two sets of removable pins.

The best thing is this kit is quite affordable and comes with a one-year warranty. Moreover, it comes with an integrated low-profile handle allowing you to remove the crank pulley conveniently.

This screen wrench holder comes with a new V2 design with an upgraded small pin.

Else, you can hire a novice mechanic to do the job. Moreover, you don’t need to spend extra bucks on hiring a seasoned mechanic.



The wobbling of the crankshaft pulley might be an early indicator of significant wear and tear or a late indicator of it.

It is absolutely necessary to conduct routine inspections of the crankshaft pulley in order to look for any symptoms of damage or wear. The adage “Prevention is better than cure” is something that everyone is familiar with.

If you choose to disregard the crankshaft pulley, you will do significant damage to the engine, the crankshaft, or the belts.

Therefore, what do you consider to be the most preferred choice? Should I get a new engine or just replace the pulley on the crankshaft?

I am aware that you are intelligent individuals who are capable of solving the problem on your own.

Take good care of your crankshaft pulley and make sure it doesn’t shake around!