Outboard corrosion could happen in a very short time if the outboard is not protected properly.
It could occur to both inside and outside of the outboard, in both freshwater and saltwater. Even rainwater could cause outboard corrosion problem!
So it’s important to learn some outboard corrosion protection tips before it’s too late.
In this post, you’ll learn how the outboard corrosion problem occurs, how to protect and repair outboard corrosion with the most effective and easy methods.
Table of content:
- 5 Most Common Corrosion on Outboard & Solutions
- 8 Effective Ways to Protect Outboard from Corrosion
- How to Remove Corrosion from Outboard Motor
Note: Most insurance policies exclude the damage caused by outboard corrosion issues. For example, the Suzuki warranty does not apply to the corrosion damage.
5 Most Common Corrosion on Outboard
Learning the types of outboard corrosion and what causes corrosion can give you a better idea of how to fight it.
#1. Simple Outboard Corrosion
If you put the metal in the water and expose it in the air, it will corrode to some degree over time. This is so commonly seen that it is called simple corrosion.
The simple outboard corrosion is actually a process of degradation where a more stable metal oxide is produced. For example, the red discoloration of rusted iron and the gray dust that forms on bare aluminum.
Solution: Boaters can easily prevent it with some outboard engine anti corrosion spray, such as the Corrosion Block. It’s one of the best outboard corrosion spray tested.
#2. Outboard Motor Galvanic Corrosion
The galvanic corrosion often occurs to bronze or aluminum propeller on a stainless-steel shaft, so outboards are at high risk.
In theory, when you have two different metals that are physically or electrically connected and immersed in water. It produces a current where the metals will give up its metal ions to the water, and therefore the outboard corrodes.
That’s why boats and outboards need sacrificial anodes.
Solution: Using a third metal (aka sacrificial anodes) is the best way to get rid of the galvanic outboard corrosion issue. When the corrosion begins, the sacrificial anode will corrode first, protecting the less active metals in the outboard motor.
#3. Outboard Corrosion Caused by Shore Power
Improper boat’s power connection could also cause outboard engine corrosion.
Boats plugged into shore power share the green ground wire with other boats in the marina. But with the green wire connected to the DC ground system, it extends to a boat’s outboard.
The outboard is therefore connected to the neighbor’s grounded underwater metals, which may be stainless steel or bronze. If not protected by an anode, the outboard will be at risk.
Solution: The solution to fight this type of outboard corrosion is to install a galvanic isolator, which will block the current that travels through the dock green wire to your outboards.
#4. Stray Current Corrosion
The voltage leak in the DC system can also cause corrosion on outboard motors.
Solution: To get rid of this type of outboard corrosion, make sure there are no other wires in the bilge, and the only wire to the bilge pump should be checked regularly to be sure it is in good shape.
Having all the underwater metal bonded to the boat’s ground can also help.
#5. Dry Corrosion
Dry corrosion occurs when there is no water to aid corrosion. And outboard exhaust corrosion is one of its common forms.
The fuel burn will produce some by-products known as sulfate salts which are highly corrosive especially in hot temperatures. If your outboard’s cooling passages aren’t cleaned regularly, there will be hot spot inside and lead to outboard exhaust corrosion.
Solution: The best way to fight Yamaha/Suzuki/Honda/Mercury outboard exhaust corrosion is to flush your engine out with clean water regularly after every trip.
And for the corrosion occurring around exhaust outlets, the marine wax could help get rid of it.
Outboard from Corrosion Prevention: A Comprehensive Checklist
So how do you stop engine corrosion?
I’ve summarized some important tips for the best outboard corrosion protection.
- Pay attention to the bubbles or blisters which is a hint of the outboard corrosion.
- Flush the entire outside of the outboard with freshwater after every use. Use some mild soap like the Wash & Wax Concentrate can help better cleaning.
- Remove the cowl and rinse the powerhead with freshwater for inside cleaning.
- Make sure the powerhead and the cowling are air-dry before re-installing the cowling.
- Apply the outboard motor corrosion spray (silicone spray) to protect the outboard surfaces and electrical connections from salt-water nastiness.
- Utilize sacrificial anodes for extra protection, make sure they are all in good shape, and replace them when there is only about 50% left.
- Install a galvanic isolator to avoid outboard corrosion issue caused by shore power.
- Replace or clean corroded parts as soon as you notice them.
Attention: Outboard saltwater corrosion is a common concern, but the fresh water also contains contaminants that can cause corrosion over time.
So be sure to flush the outboard after every use if you boat in saltwater, and periodically if you boat in freshwater to properly avoid the outboard corrosion problems.
How to Remove Corrosion from Outboard Motor
How about the outboard corrosion repair? How do you remove corrosion from boat aluminum?
If the corrosion is already there, we can use the outboard corrosion removal to get rid of it.
A good way to remove internal corrosion form an outboard block is to use the Salt Away. It mixes in with the flush water to remove the salt that has been retained in the motor from running. And for the external corrosion, try Lime Away.
If you are looking for ways to clean the calcium deposits inside the motor cooling system, you may get some ideals in this thread.