yanmar sd 20 electrlysis

[pagmd]

I"m a Canadian, boat moored in the U.S. not seen for 18 months, so not hauled out in2020 and no bottom paint dond or anode changed on a yanmar SD 20. Diver contacted in July - "can't dive as I am not an essential worker" -later found not to be true. Another diver contacted in Nov. - hedove and found electrolytic damage to the SD as the anode had 0bviously disappeared. lower unit of the SD probably needs to be replaced. I wouldn't attempt it myself but would appreciate input, so know what to expect and "oversee" the mechanic.

[tkeithlu]

The replacement is pretty straightforward. The question is whether it is necessary. If the corrosion is on the foot casting and the damage is not sufficient to threaten its structural properties, then sand, prime, paint, and install proper anodes. They will prevent future corrosion.

Then the important question to me is your maintenance thereof. The admiral will no longer allow me to dive our steel boat, so I keep a silver reference electrode on hand. It cost $130, but dropping the electrode in the water and connecting my trusty multimeter to it and to the bonding (the hull, in my case) gives a reassuring 1+ volt reading, and all is well. Nothing is corroding under the hull except my 14 aluminum anode plates. When it dropped to 0.9 volts this spring I pulled the boat. I recommend this approach to you. I hate to see your risking further expensive damage. Here's an electrode:

https://www.boatzincs.com/corrosion-...RoCWkUQAvD_BwE

[pagmd]

Thanks very much for your advice. I will certainly follow up on your suggestions.

[ggray]

get a galvanic isolator.
easy to install.