Aluminum Anodes for saltwater use

[BigDog98]

So as the season is coming closer it is time to replace all the anodes on the outdrive and every year I always debate on what type to purchase. I am thinking about purchasing some aluminum anodes instead of the traditional zinc anodes since I boat in salt water. Has anyone every used the aluminum anodes in saltwater and how did it hold up? My boat generally sits in saltwater for about 4-5 months before it gets pulled out and winterized. I clean the outdrive once a month of growth so I don't know if that will help the life of the anode. And can I mix aluminum and zinc anodes? I already purchased a set of trim tap anodes and did not realize that they are zinc so the question arises if I can mix aluminum with zinc or should they all be made of the same material no matter where it is located? Thank You

 

[BigDog98]

The outdrive is a bravo 3 so I believe it is made out of aluminum if I am not mistaken.

 

[Mohawkmtrs]

Salt water = zinc anodes (especially since the boat is in salt water for 4-5 months).

Don't mix up the anodes...they protect the aluminum of your outdrive.

 

[lg260ss]

Both Merc and Volvo recommend the aluminum anodes on their drives for salt water use. It is well documented due to the issues Merc has had with bravo 3 drives and corrosion.

 

[Mohawkmtrs]

Funny...volvo-penta.com (faq page) says zinc anodes for transom shield and stern drive in salt water.

 

[Mikeopsycho]

I've always run zinc in the salt chuck and magnesium in fresh water. To my knowledge I've never used aluminum, but who knows what you actually get from the suppliers?

 

[dingbat]

NEVER MIX Zinc and Aluminum Anodes on the same vessel.

• Zinc Alloy Anodes = Salt water only
  • Not recommended for use in fresh water
• Aluminum Alloy Anodes = Salt or Brackish water
  • Not recommended for use in fresh water
  • Proven to last longer than zinc due to increased capacity
  • Alloy is manufactured to meet or exceed US Military Specification (MIL-A-24779(SH))
• Magnesium Alloy Anodes = Fresh water only
  • Not recommended for use in salt or brackish water
  • The only alloy proven to protect your boat in fresh water

http://www.performancemetals.com/images/pdfs/ABYC 09.pdf

 

[JASinIL2006]

NEVER MIX Zinc and Aluminum Anodes on the same vessel.

• Zinc Alloy Anodes = Salt water only
  • Not recommended for use in fresh water
• Aluminum Alloy Anodes = Salt or Brackish water
  • Not recommended for use in fresh water
  • Proven to last longer than zinc due to increased capacity
  • Alloy is manufactured to meet or exceed US Military Specification (MIL-A-24779(SH))
• Magnesium Alloy Anodes = Fresh water only
  • Not recommended for use in salt or brackish water
  • The only alloy proven to protect your boat in fresh water

http://www.performancemetals.com/images/pdfs/ABYC 09.pdf

On the link you included, they indicate that aluminum is the safest bet for freshwater...

 

[dingbat]

On the link you included, they indicate that aluminum is the safest bet for freshwater...

It really depends on your expectations and criteria of "best". Do you want the best possible protection or an extended life expectancy?

Mg being more active, would provide better protection but at the cost of a reduced life time in "polluted" waters.

Al would have a longer life expectancy but at the cost of reduced protection in "freshwater".

 

[Scott Danforth]

I would rather replace the zincs often than worrying about corrosion.

 

[snowman246]

While on the topic, if a boat is only going to be in saltwater for a few days, do the anodes need to be changed? I am planning a week long trip and estimate the boat being in the water 4-5 hrs a day. I plan on rinsing the engine and outdrive after each use. Will my magnesium be ok for this short amount of time or should I replace for the short time I will be in the salt?

 

[dingbat]

While on the topic, if a boat is only going to be in saltwater for a few days, do the anodes need to be changed? I am planning a week long trip and estimate the boat being in the water 4-5 hrs a day. I plan on rinsing the engine and outdrive after each use. Will my magnesium be ok for this short amount of time or should I replace for the short time I will be in the salt?

Don't bother to change them. 35 hours of immersion is barely going to get the boat wet