JBlatt

Stern drive wrong anti fouling paint

10 posts in this topic

Hello to you all.

I have a Chaparral 204, from 2007. It has an Alpha II stern drive. Engine is a Mercruiser 4.3 MPi also from 2007.

I recently made a big mistake with the anti fouling paint. I was painting the hull and forgot to use a different paint for the stern drive. I now have the stern drive painted with normal hull anti fouling paint. The zincs are installed but I'm not sure if even so I will get galvanic corrosion.

Any ideas in this?

Thank you.

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What bottom paint did you use? If it's copious copper oxide based, you need to get it off of there.

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Hi Wingnut.

Thanks for the comment. I believe the paint has the copper oxide but looking into the galvanic potential of the materials the zinc has a lower galvanic potential which would allow it to be sacrificed instead of the stern.

What is the reason for the copper oxide to corrode the stern drive?

Thank you.

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No metallurgist here, but history rules and not understanding the chemistry not withstanding, painting an aluminum out drive with copper and putting it in salt, or even slightly brackish water has pretty disastrous results. Ask any marina. A product such as Interlux Tri-lux 33 intended for aluminum boats works well.  W

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You need to remove the bottom paint from your drive. Quickly. Or you will not have a drive left. 

brick

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Paint is Internacional Boatguard EU. It is cuprous oxide based.

Do I have to remove it even with the new sacrificial anode (aluminium) installed?

If I have to remove it what would the best way be without hurting the original sterndrive paint?

 

Again thank you for all the help and comments.

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Get it off before putting the DRIVE IN ANY WATER !!

Just sitting in water will cause damage. Keep it completely dry until you can remove the paint. Call     MERCRUISER for their advice about saving any of the original paint.  They have heard of your problem before.

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2 hours ago, cyclops2 said:

Get it off before putting the DRIVE IN ANY WATER !!

Just sitting in water will cause damage. Keep it completely dry until you can remove the paint. Call     MERCRUISER for their advice about saving any of the original paint.  They have heard of your problem before.

Copper and AL are dissimilar metals. By combining them as you did, they will act as a battery and eat each. In painting the drives, leave at least 1/2 gap between the 2 painted surfaces.   

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