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January 15, 2021

Boat Bottom Cleaning – The Hull Truth

Updated: August 30, 2022

Boats that spend most of their time in the water, unlike leisure boats usually launched for recreational day use, have to contend with barnacle buildup and marine life hitching a ride on the hull.

These extra, unwanted passengers not only slow the boat down, but the organisms can penetrate the hull and cause damage over time if not regularly cleaned with painting intervals accompanying a cleaning regimen. Continue reading below about hull cleaning and why it’s important.

What is Hull Cleaning and Why is it Important?

Left unchecked, fouling can be a real drag. Formally known as biofouling, fouling is the accumulation of sea life on a boat’s hull. Barnacle and sea life buildup can cause a boat to be slowed dramatically, overheat its engine and block intakes, all resulting in excessive fuel consumption and damage.

marine life buildup on a boat propeller

The hull isn’t the only thing that needs to be cleaned. Propellers, shafts, running gear and intakes need to be cleared and cared for as well.

Hull cleaning is the process of de-fouling and removing the sea life buildup without damaging the coating of the hull. Cleaning the bottom of a boat can be done in and out of the water.

What is the Best Way to Clean the Hull of Your Vessel?

The best way to have your boat cleaned is by an experienced/licensed boat bottom cleaning company that offers underwater services.

marine diver checking his bottom cleaning schedule

Not only will a diver clean the hull but also inspect and check for delamination, blisters, zinc anode condition, clear intakes and running gear. Hull cleaning divers will use the least abrasive materials to start such as:

  • Canvas/cloth gloves
  • Carpeting/towels
  • Light-to-heavy duty cleaning pads
  • scrapers and rotary brushes
  • pressure washers-typically ONLY for heavily fouled hardware for initial cleanings, great for thruster tunnels as well

Upon completion of the cleaning, the diver should supply you with a clear list of findings and any maintenance suggestions. Although you could perform the hull cleaning yourself, it is best to hire a professional to complete the job properly and safely.

Is Underwater Hull Cleaning Dangerous?

Busy marinas, snagged safety lines or electric shock drowning (ESD) can make in-water hull cleaning dangerous for anyone. There are many safeguards that need to be taken when cleaning the hull of your boat yourself.

yellow caution sign

More often than not it is best to hire a service to do it for you. In addition to safety concerns, there are marina rules as well as the Clean Water Act to be aware of before attempting to clean your boat hull.

To learn more about North Carolina vessel maintenance and being a clean boater, look at their state boaters guide.

How Often Should a Boat Hull be Cleaned?

Depending on where you are located will depend on how often the hull of your boat needs to be cleaned. Off the coast of North Carolina the growth rate is known to be pretty rapid, and the bottom of vessels will need to be cleaned frequently more so than other areas.

On average most boat owners will have their hulls cleaned every month. The use of less abrasive tools and monitoring buildup is key to the longevity of the paint job. If the paint is scrubbed off, this will shorten its lifespan and the ability to keep the fouling from building up.

A bottom paint job will last about 18 months to 2 years max. It is important to note that the more often the cleanings, the longer the paint job tends to last.

button link to read boat bottom paint review article

This is due to the fact that the diver will be able to use the softest brushes and pads, vs infrequent cleanings that require heavy abrasives to get the job done.

How Much Does it Cost to Clean a Boat Hull?

The cost of having a diver clean the bottom of your boat varies between areas and parts of the country. Typically companies charge by the foot, however some out there do by the minute or hour.

image of a bag of money

In general, ask around your area for respectable companies and see what they are charging, “remember” you get what you pay for so don’t jump on the cheapest game in town! There are several factors that play a role in the price of underwater hull cleaning such as:

  • length of vessel
  • time since last cleaning
  • severity of growth
  • condition of bottom paint
  • condition of the coating of the running gear

What to Look for When Hiring a Diving Company to do a Bottom Cleaning

When hiring a company to provide you with underwater hull cleaning there are a few things they must have. The first is that they are insured and allowed to work in your marina, and can always check with the Dockmaster/manager as well as other boat owners.

Most marinas also require any marine contractor to have their areas minimum insurance requirements to work there. If they carry insurance then they likely will also be legally registered as a business.

Like with any contractor you plan to have work on your vessel, make sure you do your due diligence.

underwater diver performing a boat bottom cleaning

It is not common for there to be a contract for service unless you agree to an annual maintenance agreement, some companies require it and some don’t.

I would never pre-pay any annual agreement, if they are reputable and care about the long term relationship they wish to build with you, then paying as they are serviced each time should be fine unless they have substantial savings for paying annually. Again, be sure you check references!

Pre & Post reports should accompany any service they provide as you typically can’t see the job they have done. Clear information on the job they will be performing, how it will be done, as well as presenting you with their findings upon job completion is par for the course, so ensure they provide these results with each cleaning.

Final Thoughts

To wrap this all up, regular underwater cleanings by professionals will mean less future haul outs. Monitoring your fouling growth and keeping up with your anti-fouling paint schedule are all part of creating a regular maintenance program.

Whether you keep up with the program or you let a company do it for you, you will be able to keep the running cost and maintenance down for your vessel while keeping it in top shape.

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