"PETE! this one is right up your alley... Pete to Aisle 1 to help a customer please! Pete, Aisle 1."
LOL! Sorry I've been out of commission for a few days and didn't get to respond. Glenn, how much time do you have on your hands? I can write a very long post but if you're reading it at work you might get fired

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I am a two time Mariner 28 owner, the first a 1975 model 2895 (wood superstructure, teak window frames, fiberglass hull), the second a 1980 model 2896 (fiberglass superstructure, aluminum window frames, fiberglass hull). Yours fits right in between, with the fiberglass hull and superstructure and teakwood window frames...
For looks, the old fashioned teak frames win hands down, IMHO. Also for utility on the bridge, because I love those two big opening windows and miss them dearly on my current boat. The downside, though, is that Carver never quite figured out how to get those damn things to stop leaking inside the cabin. Be sure to check under that port side settee - fold it up and look around, because my guess is you've got mushrooms growing in there right about now. I hated that on my old boat, and on my current one I love the fact that I have no leaks there and can fully utilize that extra berth under there - its my 8 year old son's "stateroom" now!!!
Another place where the old windows used to leak is on the corners of the front cabin windows. Any prolonged leaking there will stain your rugs on both sides of the hull next to the V berth...
The problem was one of design - the cabin angles INWARDS, and so do the window channels. Even with the fiberglass superstructure those old style window frames basically relied on a long piece of mahogany running the length of the cabin and a heavy dose of silicone sealer to keep the water out. Even the damn window channel drains were UPHILL from the place where the water tended to puddle. Our 2895 was bought new in '75, and by the end of '76 was leaking already...
I don't say this to scare you away from the boat, because if its cheap enough, and you're an enthusiast, you can really make that boat into something special. It just has better lines than my stubbier, stodgier model does. But those damn windows will be a bother for as long as you own the boat, so be prepared...
Regarding the "fiberglass" superstructure, Carver in those days basically used fiberglass the way Chris Craft used to use vinyl on its cabin tops - basically as a waterproof covering over a marine plywood structure. Even on my 1980 they didn't bother to seal the edges where the drip moldings are (that run over the cabin windows on each side) so of course water got in there and has pulverized some of that wood over time. My drip moldings are all coming loose and even 2" screws won't hold anymore in some places. Since I can't tip the boat upside down and flow Git Rot in there its going to take an interesting fix to straighten it out and I haven't come up with a good plan yet. Perhaps some other RO has had an idea there???
Also, on the lower part of the cabin house behind the two hanging lockers (on my boat the "Carver" emblems are there but on the '78 they were located up on the bridge sides), the same thing happened - water got in and the fiberglass outer shell lost its grip on the wood. So the damn things stick out a good inch or so from where they are supposed to be. I'm thinking of jamming a ton of 4200 or 5200 in there and bracing the thing together with a 2x4 and some clamps until it cures. That oughta work for awhile...
Speaking of all that teak, BTW - it can be Hell to take care of, but these days Cetol Marine by Sikkens Corp (available through BoatFix or your local retailer) is a real blessing to the teakwood boat owner. It makes it so much more enjoyable to maintain all that wood because it lasts soooo much longer. I used to use the orangy original color, but they now have a more natural color that I'm going to try this year...
Now, to the HULL. I want to SCARE YOU A BIT HERE so you check this out CAREFULLY. These Carver boats, model numbers that end in "5" or "6", have BALSA CORED HULL BOTTOMS. BE SURE to get this checked, and use your own intuition down there. If any of that balsa is seriously damaged that boat belongs on a BURN PILE, not in a marina, unless you are incredibly gifted at fiberglass work or are quite wealthy. Now I've owned two boats and neither of them had any problems down there, but if the prior owner(s) were overzealous and screwed around installing lots of goodies in the bilge areas without sealant then water might have gotten into places it shouldn't, and Carver really didn't do a good job back then in insuring that the wood would last if compromised in this way.
If there are problems with the STRINGERS its different, because you can fix those (I did) without harming the balsa coring in the hull, although its still a pain in the errr... "dupa" to do all that work (in my case I had to lift an engine out...
BTW if you want to see what the potential for water damage to the balsa hull coring is like, just pick up one of the engine hatches and look at the bottom. I GUARANTEE YOU that the balsa wood coring also used in that hatch has turned into soup a long time ago (I've never seen a Carver of that vintage where it DIDN'T HAPPEN!) and the damn thing is sagging. No big deal if its just an engine hatch - you can take the thing out, flip it upside down, use one of those DREMEL attachments to cut the gray colored bottom layer out and expose the coring, replace the coring either with more balsa or a piece of PTP plywood, and glue back together. But imagine if that is your hull instead!!!
Other systems to look for - the engines may be Mercruisers, Pleasurecrafts or Crusaders, or a newer repower. They may well be Ford 302 or 351s if they're twins, or a single big block if its a single inboard or I/O. I don't believe Carver offered a genset or air conditioning in '78. Inside, you may have a gas or electric range, or alcohol/electric stove. If its a gas stove be sure to check out the fuel system for it - there's a big box hanging over the transom that contains the tank. The head may well be a Mansfield (now Dometic/SeaLand) Traveler 911-M28 head which has been a great self contained system for years. The first thing I would do, if its obviously one of the older units, would be to remove it and replace with a brand new model still available from SeaLand, which is of a much sturdier plastic tank, porcelain bowl construction and has about .5 gal greater capacity than the old system. You might consider an auxiliary holding tank system too, like I installed on my boat...
Carpets, curtains and fabrics are likely to be gross if they're original, but that's the fun of upkeeping an old boat...
IMHO the Carver 28 was in its day one of the best ever for carrying families for both short trips and extended vacations on the water. Even today it still holds its own against still-produced boats like the Bayliner 28 Classic and other more-recently-extinct models. My 28s have been up the NY State Canals, Lake Champlain, the Hudson, the Jersey Shore, the LI Sound, and 20 miles off Montauk Pt, LI. They've carried rafts and floats slung to the bimini top, bicycles in the cockpit, we've cooked in the galley for yacht club events, and even strung Christmas decorations all over the boat every year for the Labor Day bash in the Rondout Creek. One thing about Carvers - they are USEFUL and they get USED! Just make sure you're spending your money on a worthwhile example...
Hope this helps...