Just like any other boat or outboard engine, there are things to do and not do to extend the life of an Honda outboard motor and boat. So here are just a few things to be ... read more aware of, and we will start with the "do’s". If you double check the anode, and it is half corroded, it is time to replace it. Don't convince yourself that it still has some corrosion life. Remember the more metal (like the metal on an outboard engine); the more opportunity corrosion attacks your anode and not other areas of your boat or outboard. Be sure to remove paint and clean the mounting surface of your anode. If your boat has trim tabs, protect them individually and do not bond. Some trim tabs are constructed of stainless steel; they can still corrode, and you will need to be aware of that.
Now we will move onto the do not's. Do not paint your anodes. It won't work and therefore is a waste of your time. Don't mix anode types. For example, aluminum anodes will try to protect zinc anodes on the same bonding circuit. With that thought, do not use zinc anodes on aluminum outdrive. Finally do not use magnesium on outdrives in salt or brackish water because it will over-protect the aluminum.
So those are the do's and do not's for your anodes. Take care that this is done, and you will maximum performance out of your anodes that then helps your boat and outboard motor. That keeps you out on the water, and that's something every boater wants.
In this section, we will briefly go over various metals that are common in the marine industry. ... read more Aluminum: It is a light, but strong metal. The best thing about aluminum is it has the best resistance to corrosion because it forms an oxide surface film. You could see white gritty powder when it's unprotected, but that's not harmful to your boat, and anodizing eliminates this. There is a slight drawback to an aluminum anode though. It's very active on the galvanic series that makes it vulnerable when it comes in contact with more noble metals such as bronze, brass, etc.
Brass: It is an alloy of copper and zinc. This metal is typically not recommended for underwater use. This metal suffers from dezincification, and this is simply the galvanic corrosion that removes the zinc out of the alloy mix. Bronze is an alloy of copper with little to no zinc. You can find most bronze in fittings and the boat. If you are used to being immersed in water, it is good to resist corrosion.
Stainless Steel: It is a widely used resistant material, and the reason for that is due to it's strong. Like aluminum, it can resist corrosion attacks because of the oxide film it develops. Make sure that your stainless steel has oxygen. No oxygen is when it's under seals or barnacles and when it has no oxygen then it loses the oxide film that makes it so durable. It is typically not recommended for underwater applications though unless it is protected.
Let's discuss a few hull options that will most likely affect you. Wood hulls are prone to problems because of rotting and corrosion caused by fittings and such. Silicon bronze fasteners are recommended for wood hull applications and be sure, not to use stainless steel below the waterline. Fiberglass recommends silicon bronze fasteners below waterline.
Finally, we will discuss steel hulls. You will need to coat for corrosion resistance and use sacrificial anodes. Be extremely cautious using magnesium anodes on steel hulls. That's your FYI about different marine metals; you can refer to this when you're making decisions about different metals on your boat.