Given my inability to post something from another source, the following was received from Steve D'Antonio, Passage Maker. Dec 16 at 0959
Thanks for your note and comments. Sliding windows have been the bane of boat owners virtually since they were first introduced, with wood frames. When aluminum frame windows were introduced, the challenges remained, albeit for different reasons.
Aluminum, as I've written on many occasions, is a wonderfully versatile maetal that lends itself well so so many onboaard structures. It does, however, have some weaknesses, chief among these is a type of corrosion knon as puoltice. Poultice corrosion occurs when aluminum remains wet and starved of ozxygen. The tracks or grooves in which your, and many other, windows slide are the ideal breeding ground for this phenomenon. The mechansim by which this occurs is twofold. One, the fuzzy weather strip material that's used in most aluminum windows is hygroscopic, it holds water, against the aluminum, that ultimately becomes stagnant, which in turn fosters the corrosion. Two, the byproduct of this corrosion, aluminum oxide crystals (it looks like greezer-burned vanilla ice cream) tends to clog the already small window track drains, whihch exacerbated the problem by retaining still more water. As an added bonus, when the drains clog water overflows the tracts and ofter runs inboard, into the boat.
Preventing the problem involves routinely washing out the tracks with fresh water and making certain drains are clear. If the windows have become lodged in the tracks, as you have, freeing them can be a challenging. Dissolving or loosening years' worth of aluminum oxide can be difficult. Initially, I'd try a penetrating solvent such as PB Blaster. Spray it into the tracks and let it remain for a few hours. If that doesn't work, you may wish to try something more agressive. Contact Trac Ecological, they offer a line of products designed to clean and descale aluminum and oather metals used in marine cooling systems. The my be applicable for this application as well. www.trac-online.com
Once the windows are free, you may find the tracks do not need to be replaced. If they do require replacement, the frames would need to be removed from teh cabin, tough to do without damaging them, disassembled and the bottam track protion replaced, a process that is typically economically infeasible. At that point, the only practical solution is complete window/frame replacement.
My comments: This reply took less than 24 hours: Not a very satisfactory answer to the issue, but Steve has, as others have found, articulated an issue which we all face. Being on fresh H20 has its merits, but like the wooden sailor's dry rot of any sort spells $$'s to resolve the problem. The only point I suppose is to undertake the washing with the products suggested, but the short and long of it is that window function as well as water mark noting becomes a first IA when viewing a boat for potential purchase. Soldier on and solve the problem, $$ in hand, as well as labor