I just noticed all the notifications for this topic.
I am the original poster seeking help with my corrosion problem on my 04 Alumacraft Navigator 175. I lost a few nights sleep over the deal, then I called Alumacraft in St. Peter and talked to them.
They were wondering if I had an onboard battery charger, which I said I did. They said improper installation could be the cause, but at any rate they would need to inspect it and I would have to leave it for 2-3 months so they could decide course of action. I told them that once they figured it out, I wanted to have a quote before they fixed anything which they said they would do.
The boat sat down there for about 4 months. One day I got a call and they said it was ready for pickup. I asked what they ended up doing and they said they replaced the entire transom. I had a sick feeling in the pit of my stomach when I asked what the bill was? They said that Alumacraft had a 1x fix on any product defects or faulty workmanship, and mine fell into these categories.
They never said exactly what caused the corrosion, but in the end materials and labor were covered by Alumacraft and my cost was $0.00.
WS