First reflex: Walk away
. Or offer $1000 firm. The world is full of SJ21s in ready-to-sail condition
for ~$2000. Two thousand to $2500 is the going rate, tho some ask much more or much less. They sell for $3k in minty condition with spanking-new sails and a new outboard.
The C22 mast is wrong for this boat in more ways than I can enumerate -- but the two most critical are weight (you really want to put that much excess mass up high, on a boat already known for tenderness? It might capsize!) and stiffness. Most SJ21s are retrofitted with backstay adjusters, which bend the mast ~6" to depower the main. You do not want to mess that geometry up. Oh, and the spreader rake is different on a C22 mast.
If you can get the boat for $1k and buy the factory rig for another $1400, that might
be worthwhile. You don't want to know what truck freight would be on that mast, tho -- I'd guess $600 via common carrier.
So just in case you are still eager, here's some other things to look for on the SJ21 to make sure it's as pristine as claimed:
* Soft decks. Nearly all SJ21s have (or had at some time) wet balsa in their decks, ranging from "a few inches around the jib tracks" to "oh my God, the whole thing is saturated."
Clark did not use adequate backing plates nor isolate or bed the hardware correctly, and few owners have attended religiously to rebedding. Look for any signs of brown stains, weepage, or crusty white stuff around the fasteners on the cabin roof. Walk on the deck, especially around the mast step, grab rails, and winches; it should exhibit no give at all. Recoring a deck is not the worst job in the world, but wet decks would further reduce the market value of this
boat to near zero.
* Wet transom. Ditto on the balsa. The port 2/3rds of the transom is balsa cored and often soft around the rudder gudgeons and motor bracket (but not the backstay chainplate, which is not in the cored area.) The transom is, in its way, a worse recore job than the decks -- and a safety issue to boot.
* Swing keel. It's hard to tell if the keel or its pivot is in good shape. Look for signs of repair around the pivot bolt; it is bedded in brittle polyester resin, surrounded by plywood that is often wet due to leaking keel gasket screws. I tore mine apart last year and was appalled at the condition of both the plywood and the pivot assembly. If it HASN'T been repaired, assume it needs to be. (This is another common problem.)
* Rudder. The original kick-up assembly was garbage: heavy & badly-shaped. An aftermarket rudder assembly adds value, but many are not legal for 1-Design racing. Much blood was recently spilled over this issue within the class.
* Hardware. The original stuff was Ronstan -- not bad for its time, but many blocks and sheaves are past their sell-by dates. The jib blocks and keel-winch sheave deserve close scrutiny. Replacement of all essential blocks and cleats will ding you $600. I know this cuz I just did it.
* Shroud chainplates and bulkheads. Not really a problem on the Mk1, but Mk2s and Mk3s were prone to leaks and rot around the chainplates. Try to ascertain how well the chainplate bedding has been attended, and look for any sign of water intrusion where the bulkheads are tabbed to the deck & hull. That repair is a big deal and requires mad skills. The damaged mast sets off warning bells -- did a shroud pull loose?
That's it! It's a simple boat whose problems are well-documented. The SJ21 class, once moribund and poorly organized, seems to be waking from its stupor and trying to build fleets again. I hope you buy one and enjoy it as much as we love ours.
But remember: This is a $2000-2500 boat when its problems are few. As a new sailor buying your first boat, I really really urge you to shop around and find one that can be sailed as is and needs no urgent refitting. Sail a little, fix a little. Dat's my recipe for happiness.