Symptoms of Outboard Mounted Too Low or Too High (Explained)

Summer is the best time to go boating with family, and we cannot deny that there are a lot of freshmen purchasing their first boats. And they need guidance in identifying issues like symptoms of outboard mounted too low and too high. 

Symptoms of outboard mounted too low and too high could be noticed by porpoising, steering problems, excessive dragging, and many more. 

Before you go on a trip, it’s important to orient yourself by reading this article to recognize and solve issues from your motor right away!

Outboard Motor Height

In buying a boat, we had to consider a lot of things aside from its physique and beauty. There are a lot of new things to learn and responsibilities to maintain a boat.

Now, here in this article, we’ll guide you on how to have a proper transom height to avoid negative experiences while on a trip.

Uneven transom height creates aggravating problems. Too high or too low can affect the propellers, outboard motor, and bracket.

To have an accurate calculation of the transom’s height, it should start from the bottom of the hull towards the gunwale at the transom.

Since motors have various sizes, boat builders from the 1960s formulated a standard measurement that corresponds to the boat’s transom height.

These are so-called motor shaft lengths. Note that the longer the motor, the longer the driveshaft should be, but it does not clarify the exact size.

Symptoms of Outboard Mounted Too Low and Too High

The sizes are coded with S, L, XL, XXL categories. S for short with 15 inches, long (L) with 20 inches, XL with 25 inches, and XXL with 30 inches length.

With the use of clamp brackets, adjustments to the motor’s mounting height can be done. The top portion of the bracket has at least 6 hoes of 0.75 inches spacing.

Through this, boat owners can easily adjust the transom height of the outboard motor according to recommended shaft height.

Even if most boat owners have known this information, they tend to forget and neglect these factors which result in faulty operation.

How to identify if the outboard is mounted too high or low?

Having inadequate knowledge of the equipment is the reason why boat owners tend to have difficulty finding out the accurate mounting height.

Although it’s never certain and depends on shaft lengths, some owners use luck to find the perfect placement of the outboard in just one trial.

So much about fortune, there’s an indicator that could distinguish whether the motor is attached correctly or not, and it’s called an anti-cavitation plate.

These flat plates are found beneath the boat. which serves as a planning surface that improves the boat’s performance.

Moreover, this prevents air from being trapped, thus maintaining its exact height and steady flow while boating.

Here are the steps to ensure proper height placement through an anti-cavitation plate.

  1. Look for an eight to ten inches long straight edge along with two by four length.
  2. Then lower the outboard to be ready for positioning.
  3. Grab the straight edge and place it in a lengthwise position against the base of the hull. This will provide access to at least 2’ or 3’ space towards the outboard.
  4. Examine the arrangement of both the anti-cavitation plate and straight edge. Ensure that the plate lies above the straight edge.

Symptoms of an Outboard mounted too low

When there’s a problem, there should be a reason behind it. Let us find out the most frequent signs behind mounting the Outboard too low.

Excessive Dragging

Mounting too low can hold back the boat from speeding up.

Instead of moving forward, the motor’s height affects the force pressure to push the boat, thus dragging and halting the movement.

Excessive Kicking

Kicking an excessive amount of water is another sign where the outboard is mounted too low. By visual observation, you can directly assess that the outboard should have a smooth and adequate release of water.

Limited Speed

Failure to run the boat at its top speed is already a sign although it’s hard to recognize immediately especially when you’re new to the field of fishing or boating.

For veterans, it is easy for them to determine any alteration in their outboard’s speed compared to its last usage. This is where they can conclude that the outboard might be mounted at an inappropriate height.

Poor Control

Another indicator is an insufficient effort in handling an outboard. Poor management could result in a lot of risk factors such as making a mistake in mounting could even decrease its capability to run properly.


Porpoising is the monotonous bouncing movement of the boat’s bow even while boating in nautical conditions. One factor that may have caused this is the mounting of the outboard lower than recommended.

Water Forcing into the Outboard Cowling

A cowling served as a protective covering of the outboard motor. So, less water should penetrate the engine. When it has reached this, your outboard might be placed in its lowest level and needs adjustment.

Symptoms of an Outboard mounted too High

Mounting too low is bad, well mounting too high is also not good. Here are some signs to keep track and identify whether your outboard is mounted too high.

Less Dragging

As the outboard is higher, it gets closer to the surface. This signifies decreased pressure between the motor and water. Therefore, moving forward will be lightweight and allow your boat to speed up.


Just like when mounting too low, higher outboard can still result in porpoising. But this will tilt the position of the boat which enables you to aim at the full potential speed of your boat.

Propeller Ventilation

Mounting too high can affect the job of the propeller. As it gets higher, it leads to decreased water pressure. Hence, it exposes the force controlling the boat and will likely ventilate above the surface then affect its speed.

Steering Problems

Sometimes, mounting too high allows fastening your water venture. However, too much speed could also overwhelm the driver, consequently losing control in steering the boat.

How often should you change the mounting height of the outboard motor?

In general, a normal functioning outboard mount lasts 5 to 7 years. However, if the symptoms arise, you can inspect it frequently, and changing the mounting height is possible.

Aside from the outboard, check the transom, gauges, and other parts connected to the motor. Assess for any build-up of corrosion or faulty gauge switches. Alter damaged parts and cleanse the boat as part of its maintenance.


The bottom line of this discussion is that proper installation of transom height and outboard must be always considered. Use our guide to discover symptoms of outboard mounted too low and too high.

Leave a Comment