Symptoms of Outboard Mounted Too Low or Too High:(All Signs)

Your new boat may come with power pre-installed for optimized performance. However, in many cases, dealers mount the outboard as it comes uninstalled.

Although they know their job well, you have to ensure you know the logic behind their advice. This is why you need to look out for symptoms of too high or too low mounted outboards.

In this article, I will teach you just that in detail.

Signs To Detect an Incorrect Height for Mounting an Outboard?

Depending on the condition of your boat, your outboard may need a change of height. These signs are given below:

  • The condition of the transom has changed (especially in the case of old boats). The transom’s height might have changed due to a deteriorating condition.
  • Defective marine bedding compound where outboard is mounted.
  • Worn down hardware that was used to hold the outboard. Sometimes high-strength sealants also cause height fluctuation for a mounted outboard.
  • The outboards have mounting holes that are vertically aligned. After attachment, the outboard may look like it’s dangling. This suggests problematic adjustment.
  • The comparative size of the gear case for a new engine may require a change of height.
  • The cavitation plate on the outboard (if present) is not level.

What Are the Symptoms of an Outboard Mounted Too Low?

Here are a few symptoms of an outboard being mounted too low:

Excessive Drag

This holds back your boat from achieving its full potential.

Drag or hull drag is when the total force or net force opposes the forward movement of the boat. It is because of the shear force and pressure acting on the surface of the hull.

This is the very reason why a boat doesn’t reach enough speed, that is, low RPMs.

More the area of the outboard underwater more will be the drag. This suggests that the outboard is too low.

Poor Control

You face difficulty adjusting the speed of your boat according to the waves. Of course, know that your experience isn’t failing you.

But your outboard may be.

Difficulty handling the boat is a sign of lower mounted overboard.


Porpoising is when the bow of the boat is springing up and down. This happens when speed cuts down. And that is the result of a low mounted overboard.

Excess Water Sprays

The outboard may be shooting out more water than normal.

Water on the Cowling of Motor

If the overboard is too low, water can seep in. This is apparent in water collecting on the cowling of the motor.

What Are the Symptoms of an Outboard Mounted Too High?

Here are a few symptoms of an outboard being mounted too high:

Unleveled Plane

When you want to plane out the boat, the prop blows out. This fails to plane the boat. This is the most common sign of a high overboard.

Cavitation on Hole Shot

Cavitation is the increased RPM as more air flows over the prop.

Cavitation creates gas bubbles underwater. Due to cavitation on the hole shot, the hole shot is not as clear. This happens when the outboard is mounted too high.

Less Drag

When the outboard is mounted higher, there is lesser motor present underwater.

That means, the body faces less pressure against forward speed, resulting in less drag.


For the overboard being higher, the tilted position will cause porpoising. This leads to you boat breaking contact with water. This also enables you top speed!

Low Water Pressure

When you are running the boat, you seem to slip the prop. You are not getting enough water pressure. This tends to happen when the overboard is too high.

Position of the Anti-Ventilation Plate

When the boat is trimmed down completely, the bottom of the anti-ventilation plate is supposed to be roughly 1″ above the keel per foot distance to the transom.

Consistent Ventilation of the Prop

The prop ventilates whenever going down a steep wave.

How Should You React If You Detect an Inappropriate Height of the Overboard?

You can try moving forward the fuel tank or the battery and other equipment.

To avoid porpoising, consider trimming the boat.

In case you are rebuilding the boat, consider rebuilding a broken transom. Rebuild it to a proper level. You can check the level with the help of a cavitation plate.

Consider replacing the prop as well.

Is Fixing the Overboard Height Typically Expensive?

It totally depends on what things you are changing.

If you have to replace the hardware holding down the marine bedding on which the motor is mounted, then it might be moderately costly.

But if you are rebuilding everything from scratch, it might be very expensive. Rebuilding the transom can prove costly too.

How Often Should You Inspect the Mounting Height of Your Overboard?

If you have read up to this point properly, then you already know the answer. There is no specific interval. However, you should know that engine mounts typically last for 5-7 years.

The transom may need checking from time to time of corrosion. The water pressure can be checked with a pressure gauge (install one in your boat if you haven’t).

When you see the symptoms of high or low mounted overboard, then you should fix it.

If you are taking an old boat, then check the engine level before sailing. This is all very general anyway. There is no specific interval after which you should be checking engine levels.

The Verdict

Many people mount their outboard motor higher to gain more speed. However, that often wears out blade paint.

Moreover, trimming and porpoising are common things that need to be taken care of.

The boat can go out of control if the engine heights are extremely changed than normal.

Therefore, optimum engine heights should be maintained by all boat owners for proper regulation.

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