This parallels something I just posted in the general section, but I wanted to put something here with a bit more detail specific to the Macs.
Iron hates being iron. It always dreams of one day getting married to oxygen and becoming Iron Oxide, and will take the first opportunity to do so. “Surface rust” never stays that way. You can see in my photo’s that the prior decades of owners appeared to slop blue bottom paint on the keel while in the retracted position, likely on the trailer. The bits of keel in the trunk may have never been painted since the boat left the factory.
The keels on Mac 25s are iron to keep costs low, and that cost cutting did not stop there. Mac sourced the keels from the cheapest casting house possible. Look closely and you may still see “MEXICO” cast into the side of yours. Now, Mexican shops can make some damn find castings, many iconic modern muscle motors have Mexican castings… but that wasn’t 1984, that wasn’t this shop.
Part of why the pitting problem is so bad is because the thinner areas of the casting have a -LOT- of slag inclusions, seen as black spots at the base of the pits. These nodules of not-iron, as well as voids, greatly exacerbate rust problems in the future because they provide a lot of internal pathways and surface area for water exposure. You’ll also notice that they filled a giant void in the side of my keel with some kind of mortar or bondo. So, the shop apparently used low quality materials, only heated it just enough to flow, and dumped it into the sand casting, with the gate probably being at the fat end of the keel.
This is extra bad for the Mac keel design, since all the stress is happening at the thin end, where the less-hot iron, replete with slag that they didn’t skim off before the pour, flows and settles. My keel pivot hole is a gnarly oval because it had inclusions surrounding it, offering no strength and giving rust a vector to do major damage. That pivot hole is drilled, in my opinion, way too close to the edge of the keel. This was likely done to lower the keel trunk and increase floor space, but it shortens the life of the keel.
Iron hates being iron. It always dreams of one day getting married to oxygen and becoming Iron Oxide, and will take the first opportunity to do so. “Surface rust” never stays that way. You can see in my photo’s that the prior decades of owners appeared to slop blue bottom paint on the keel while in the retracted position, likely on the trailer. The bits of keel in the trunk may have never been painted since the boat left the factory.
The keels on Mac 25s are iron to keep costs low, and that cost cutting did not stop there. Mac sourced the keels from the cheapest casting house possible. Look closely and you may still see “MEXICO” cast into the side of yours. Now, Mexican shops can make some damn find castings, many iconic modern muscle motors have Mexican castings… but that wasn’t 1984, that wasn’t this shop.
Part of why the pitting problem is so bad is because the thinner areas of the casting have a -LOT- of slag inclusions, seen as black spots at the base of the pits. These nodules of not-iron, as well as voids, greatly exacerbate rust problems in the future because they provide a lot of internal pathways and surface area for water exposure. You’ll also notice that they filled a giant void in the side of my keel with some kind of mortar or bondo. So, the shop apparently used low quality materials, only heated it just enough to flow, and dumped it into the sand casting, with the gate probably being at the fat end of the keel.
This is extra bad for the Mac keel design, since all the stress is happening at the thin end, where the less-hot iron, replete with slag that they didn’t skim off before the pour, flows and settles. My keel pivot hole is a gnarly oval because it had inclusions surrounding it, offering no strength and giving rust a vector to do major damage. That pivot hole is drilled, in my opinion, way too close to the edge of the keel. This was likely done to lower the keel trunk and increase floor space, but it shortens the life of the keel.
