I think they are called MGB now. Located about 20 minutes from me. I have seen their Duramatic and Grumman boats at some dealers, but not the swamp dragon.
Also part of their story, some ex employees went off and founded Discovery Marine in nearby Preble NY. They then became DMI (Discovery Marine Inc), which is what my 1648 is. Latter became Misty Harbor and moved to Indiana. I believe they only make pontoons now under the Viaggo name. Maybe the V and Jons moved under the Polar Craft name?
Our small lake dealer has sold their boats for as long as I can remember. They have the Duramatic V boats, Grumman canoes, and Viaggo pontoons, now. There are many old Discovery jons still in operation there. They were called Polaris jons then. My 1995 had the PT transom, which caused "worm tracks" and pin holes in the aluminum. I suspect that the earlier made Polaris's did not use PT, or they would be in sad shape by now. Anyway, it seems that a number of companys made the mistake with PT.
I've seen quite a few used Discovery boats around here but most are pretty battered or rotted. The few I've run across looked to be pretty low end. They don't seem to do well in the salt.
For me its Mirrocraft or Starcraft or any of the Starcraft sister brands.
I had a try at a Sea Nymph in the early 90's. I got it cheap and soon found out why. I saw a few corrosion bubbles in the transom when I got it but the thing felt strong. I could stand on the lower unit the transom didn't flex. The boat had come from Oklahoma by way of Kentucky and Tennessee before I got it. I bought it knowing the lower unit was trashed but the 1984 70hp ran great. It needed new carpet and some electrical work which was no big deal.
I borrowed a lower unit from another motor and took it to the river for a quick test run. The thing leaked like a sieve, there were small holes everwhere and a crack up front on the bow. I had what I first thought was water leaking in around the lower motor bolts but after pulling the motor I realized the area beneath the motor was rotted from the inside out.
After four weeks of cutting and replacing metal, $200 in paint , $250 in carpet and glue, some new wood for the transom and two full sheets of aluminum and enough welding to give myself a pretty serious tan it was fixed. I ended up cutting out the entire transom panel and welding in a new piece of 6061. I ended up having issues welding the old metal and ended up adding more inner supports as well. Never again. It in no way was worth all the work even if I had most everthing on hand at the time.
Even after it was all done, or at least done enough to at least use and get out fishing it was never the boat I had hoped it would be and me and that thing parted ways early on once it was done.
Its now a brand I avoid, along with the same era Grumman and Lowe boats.
I've also seen similar rot in the larger Mirrocraft boats in that era but after some research I found that Lowe was building hulls for many other brands in the 89's as well. The smaller narrow gunwale models were not affected from what I've seen.
I've been told that the issue is only really serious in saltwater but in freshwater there's other factors as well that create the same issues. Freshwater may lack salt but other minerals are also often present as is fertilizer runoff, sewage runoff, and water treatment and its additives that can make their way into our waterways.
The problem with copper and aluminum is that even when dry they can react. Saltwater and contaminants only speed it up. Its not a mater of if but when and how fast.
Having enough sacrificial anodes on the hull would slow it down but not eliminate it.
Do google search on Sea Nymph transom rot to get an idea of what you could be dealing with.
