Aluminum Boat Hull Care & Inspection

The hull is the foundation of every aluminum fishing boat.

Seats can be replaced. Electronics can be upgraded. Flooring can be rebuilt. Motors can be changed.

None of those things matter very much if the hull underneath them isn’t being properly maintained.

Fortunately, aluminum boats are remarkably durable. With reasonable care, a quality aluminum hull can provide decades of service.

The key is paying attention.

Most hull problems don’t begin as catastrophic failures. They start as a loose rivet, small crack, damaged coating, developing corrosion or an area that’s repeatedly being stressed.

The Tin Can Boat Works Aluminum Hull Care & Inspection Guide is designed to help owners recognize those conditions early.

The goal isn’t to make your fishing boat perfect.

It’s to know your hull well enough to recognize when something changes.

Quick Aluminum Hull Inspection

Periodically walk around your boat and check the following areas.

Exterior Hull

• New dents or creases
• Cracks
• Loose or damaged rivets
• Damaged welds
• Split seams
• Corrosion or pitting
• Deep scratches or gouges
• Damaged chines
• Previous repairs
• Loose hardware
• Damaged paint or coatings

Underneath the Boat

• Trailer-bunk contact areas
• Roller contact areas
• Keel
• Chines
• Rivet lines
• Welded seams
• Drain area
• Areas showing unusual wear

Inside the Boat

• Water accumulation
• Corrosion
• Loose fasteners
• Cracks around structural members
• Flooring movement
• Damaged supports
• Signs of leaking rivets or seams
• Areas where wood contacts aluminum

Transom

• Unusual movement
• Cracks
• Loose hardware
• Corrosion
• Separation
• Damaged braces
• Deteriorated transom material
• Movement around the outboard mounting area

If something looks different from the last time you inspected it, take a closer look.

Learn What Normal Looks Like

One of the best things you can do as an aluminum boat owner is become familiar with your own hull.

An older fishing boat may already have:

• Dents
• Scratches
• Discoloration
• Old repairs
• Minor imperfections
• Paint damage

Those aren’t necessarily problems.

The important question is:

Is this new?

A dent that has been there for fifteen years and hasn’t changed is different from a crease that appeared after you hit a submerged stump last weekend.

Photographs can help.

Taking occasional pictures of the hull, transom and known repaired areas gives you something to compare against later.

For a documented Tin Can build, photographs taken during the rebuild can also provide a useful baseline for future inspections.

Inspect the Hull After an Impact

Aluminum fishing boats are often used in places where contact with the environment is part of fishing.

Stumps.

Rocks.

Shallow bottoms.

Boat ramps.

Docks.

Submerged objects.

A minor scrape doesn’t require a crisis.

But after a significant impact, inspect the area before simply assuming the boat is fine.

Look for:

• Creasing
• Cracking
• Distortion
• Damaged welds
• Loose rivets
• Split seams
• Damaged structural members
• Coating damage

Pay particular attention to chines and other areas where the shape of the hull changes.

These areas may experience significant forces during an impact.

Dents Aren’t Automatically Structural Problems

If you use an aluminum fishing boat, eventually it’s probably going to acquire a few battle scars.

A shallow dent or scrape may be primarily cosmetic.

More concerning conditions include:

• Sharp creases
• Significant distortion
• Cracks originating from the damaged area
• Damage extending across structural features
• Separated seams
• Damaged welds
• Multiple loose rivets around the impact

Don’t judge damage only by how ugly it looks.

A large shallow dent may sometimes be less concerning than a small sharp crease located in a highly stressed area.

If you’re uncertain whether damage affects the structure of the boat, have it properly evaluated before continuing to operate it.

Inspect Rivets Regularly

Riveted aluminum boats have been catching fish for generations.

A riveted hull isn’t automatically inferior because it contains hundreds of mechanical fasteners.

Those rivets should still be inspected.

Look for:

• Missing rivets
• Loose rivets
• Damaged heads
• Movement
• Corrosion around rivets
• Water staining
• Evidence of previous sealant
• Leaking along rivet lines

One leaking rivet isn’t the same as an entire hull coming apart.

But leaks can indicate movement or deterioration that deserves investigation.

If you repeatedly find water in the boat, determine where it’s entering rather than continually accepting it as normal.

Pay Attention to Seams

On riveted boats, seams deserve the same attention as individual rivets.

Inspect for:

• Separation
• Movement
• Missing fasteners
• Corrosion
• Failed sealant
• Evidence of repeated repairs

If someone has previously covered an entire seam with large amounts of sealant, don’t automatically assume the problem has been solved.

Sometimes sealant hides the symptom without addressing why the joint is moving or leaking.

Understand the cause before deciding on the repair.

Inspect Welded Hulls for Cracks

Welded aluminum boats eliminate many of the rivets found in traditional hull construction, but welded boats still need inspection.

Pay attention to:

• Welded seams
• Corners
• Brackets
• Transom connections
• High-stress areas
• Areas around previous repairs

Look for cracks in the weld itself and immediately adjacent to it.

A crack near a weld can indicate stress, fatigue, impact damage or another underlying problem.

Repeated cracking in the same location deserves more investigation than simply welding the crack again.

The question should be:

Why is this area cracking?

Watch for Aluminum Corrosion

Aluminum doesn’t rust like steel.

That doesn’t mean it can’t corrode.

Aluminum naturally forms a protective oxide layer, but certain conditions can lead to more serious corrosion.

Watch for:

• White powdery deposits
• Pitting
• Surface deterioration
• Bubbling beneath coatings
• Corrosion around fasteners
• Deterioration around electrical equipment
• Corrosion where different metals meet

Light surface oxidation and significant pitting are very different conditions.

Pitting means material is being lost.

The deeper and more widespread the pitting, the more seriously it should be treated.

Dissimilar Metals Matter

Aluminum boats contain plenty of hardware.

Problems can develop when aluminum is placed in electrical contact with certain dissimilar metals in the presence of an electrolyte such as water—particularly saltwater.

This can contribute to galvanic corrosion.

That’s why randomly replacing hardware with whatever happens to be in the garage isn’t always a good idea.

Fasteners, fittings and electrical installations should use materials and installation practices appropriate for aluminum marine construction.

Also inspect areas around:

• Stainless hardware
• Electrical grounds
• Battery systems
• Added accessories
• Homemade modifications
• Aftermarket brackets

The issue isn’t simply that another metal touches aluminum.

The entire material combination and installation environment matter.

Pay Special Attention Around Batteries

Battery compartments are one of the places we’d inspect closely on an older aluminum boat.

Look for:

• Corrosion
• Discoloration
• Pitting
• Damaged paint or coatings
• Loose battery boxes
• Leaking or damaged batteries
• Corroded terminals
• Damaged cables
• Improper electrical connections

Batteries should be properly secured.

If you find unexplained corrosion in a battery compartment, don’t simply clean it and forget about it.

Determine why it developed.

Wood and Aluminum Need Attention

Many aluminum boats contain wood.

Transoms, flooring, decks and storage systems may all incorporate plywood or other materials.

Problems can develop when moisture remains trapped between wood and aluminum, particularly when unsuitable materials or treatments are involved.

When accessible, inspect areas where wood contacts the hull for:

• Trapped moisture
• Corrosion
• Deterioration
• Loose fasteners
• Damaged coatings

A floor that looks perfectly good from above can sometimes hide a very different environment underneath.

Inspect the Transom

The transom deserves its own detailed resource, but it should always be part of a hull inspection.

Look for:

• Movement
• Flexing
• Cracks
• Loose fasteners
• Corrosion
• Damaged braces
• Deteriorated wood or core material
• Elongated mounting holes
• Separation between components

If an outboard is installed, observe the transom while reasonable pressure is applied to the motor.

The transom shouldn’t appear to move independently from the surrounding structure.

Changes in transom movement deserve attention.

A transom problem is much easier to address before it becomes a structural failure.

Check the Drain and Through-Hull Fittings

Any opening through the hull deserves periodic inspection.

Depending on the boat, that may include:

• Drain fittings
• Livewell plumbing
• Bilge discharge
• Intake fittings
• Other through-hull components

Check for:

• Loose fittings
• Cracks
• Failed sealant
• Corrosion
• Damaged hoses
• Loose clamps
• Evidence of leakage

Sometimes water inside a boat isn’t coming through the aluminum hull at all.

It’s coming through something installed in it.

Look Under the Boat

Some of the most important hull areas are also the least convenient to inspect.

Get underneath the boat periodically where it is safe to do so.

Pay particular attention to where the hull rests on:

• Trailer bunks
• Rollers
• Supports

Look for:

• Unusual wear
• Deep scratches
• Dents
• Deformation
• Exposed fasteners
• Damaged bunk material
• Corrosion
• Areas where water remains trapped

A damaged trailer bunk can continually attack the same spot on the hull every time the boat is transported.

Fixing the trailer may be part of fixing the boat.

Keep the Hull Clean Enough to Inspect

A fishing boat doesn’t need to win a boat show.

But layers of mud, vegetation, fish residue and grime make inspection more difficult.

Periodically cleaning the hull lets you actually see what’s happening underneath.

This is particularly important after saltwater use.

Freshwater rinsing helps remove salt and contaminants from:

• Hull surfaces
• Hardware
• Transom
• Trailer
• Trolling motor
• Other exposed components

Cleaning isn’t just cosmetic.

A clean enough boat is an inspectable boat.

Be Careful With Cleaning Chemicals

Don’t assume a cleaner is safe simply because it removes stains.

Some aggressive cleaners can attack aluminum, discolor surfaces or damage coatings.

Before using a chemical on your boat:

• Confirm compatibility with aluminum
• Confirm compatibility with coatings
• Follow manufacturer instructions
• Use the recommended concentration
• Test an inconspicuous area when appropriate
• Rinse as directed

Avoid experimenting with aggressive acids, alkaline cleaners or other chemicals when you don’t understand how they’ll interact with the hull.

Making aluminum brighter isn’t worth damaging it.

Protect Painted and Coated Surfaces

Many aluminum boats have painted, powder-coated or otherwise finished surfaces.

Inspect coatings for:

• Chips
• Scratches
• Blistering
• Peeling
• Bubbling
• Corrosion developing underneath

A scratch in paint isn’t necessarily an emergency.

But damaged coatings can expose the aluminum underneath to a different environment.

Use compatible repair materials and follow the coating manufacturer’s recommendations when maintaining finished surfaces.

Don’t Seal Over a Problem You Haven’t Identified

This is worth emphasizing.

If your boat leaks, the first step shouldn’t automatically be:

Buy a tube of sealant.

Find the leak.

Determine whether it’s coming from:

• Rivet
• Seam
• Weld
• Crack
• Drain fitting
• Plumbing
• Transom hardware
• Another penetration

Then determine why it’s leaking.

A sealant may be part of an appropriate repair.

It shouldn’t be used to avoid understanding the problem.

Keep Water From Sitting in the Boat

Water that remains trapped inside a boat can contribute to:

• Corrosion
• Mildew
• Deteriorated flooring
• Waterlogged materials
• Electrical problems
• Added weight

Store the boat so water can drain appropriately.

Keep drain paths clear.

Open appropriate compartments so moisture can escape.

If you use a boat cover, make sure the cover doesn’t create a permanently damp environment underneath.

Keeping rain out while trapping moisture inside isn’t much of a victory.

Saltwater Requires More Attention

Aluminum boats can absolutely be used in saltwater when they’re properly equipped and maintained.

But saltwater increases the importance of corrosion prevention.

After saltwater use:

• Rinse the hull thoroughly with freshwater
• Rinse the trailer
• Rinse appropriate hardware
• Follow outboard flushing procedures
• Rinse the trolling motor as recommended
• Inspect electrical connections
• Watch for developing corrosion

Don’t wait until white corrosion is spreading across components before deciding saltwater might require a little extra maintenance.

Keep Modifications in Mind

Any time equipment is added to an aluminum hull, think about what the installation does to the boat.

That includes:

• Drilling holes
• Adding fasteners
• Adding brackets
• Installing wiring
• Adding batteries
• Adding decks
• Adding storage
• Changing weight distribution

A modification should solve one problem without creating another.

Before drilling into the hull, understand what’s behind the location and how the penetration will be sealed and protected.

Before adding significant weight, understand the boat’s capacity and how the weight will affect stability and performance.

How Often Should You Inspect an Aluminum Boat Hull?

There isn’t one inspection interval that fits every boat.

A boat used several times a week in shallow water experiences a different life from one used six weekends a year on a protected lake.

A practical approach is to perform:

Quick inspection: Before and after normal trips.

Closer inspection: Periodically throughout the fishing season.

Detailed inspection: At least as part of your regular annual or seasonal maintenance routine.

Also perform a closer inspection after:

• Significant impact
• Grounding
• Trailer incident
• Discovery of unusual water intrusion
• Major modification
• Long-term storage
• Purchase of a used boat

The harder the boat is used, the more attention it deserves.

Keep a Simple Hull Record

You don’t need an elaborate maintenance database.

A simple record can include:

• Date
• Area inspected
• Problem found
• Repair performed
• Photograph
• Materials used

Photographs are especially valuable for corrosion, cracks and repaired areas.

They allow you to compare the same location months or years later.

For serialized Tin Can builds, the Digital Owner’s Manual can provide the original build information and specifications as a reference point for future maintenance.

When Should You Get Professional Help?

Routine cleaning and visual inspection are normal owner maintenance.

Structural repairs are another matter.

Consider qualified evaluation when you find:

• Structural cracks
• Significant weld cracking
• Severe corrosion
• Deep or widespread pitting
• Major hull distortion
• Damaged structural members
• Significant transom movement
• Repeated cracking
• Extensive seam separation
• Repairs beyond your experience

A fishing boat isn’t the place to learn whether a questionable structural repair was “probably good enough.”

If the condition could affect the safe operation of the boat, get it properly evaluated.

Small Problems Are Usually Easier to Fix

The purpose of inspecting an aluminum hull isn’t to become worried about every scratch.

It’s the opposite.

Knowing the boat’s condition gives you confidence in it.

You know which dents are old.

You know where previous repairs were made.

You know what the transom normally feels like.

You know how much water normally appears in the bilge.

And when something changes, you notice.

That’s how small problems stay small.

Take care of the hull underneath everything else and an aluminum fishing boat can keep doing what it was built to do for a very long time.

Tin Can Boat Works

Small Boats. Serious Fishing.