Howdy,
I believe 3 different Cobras were called "King"
1. Dog-Clutch Cobra behind the Ford 460. Not really a "bad" drive per se'.......but they only made a "few" of them and not all the internal parts are still available.
2. Cone-Clutch Cobra behind the 460 & 454. Good drive too but more parts are not available. Including the impeller. If you have a good one, you need to either pay ridiculous prices for a new (old-stock) impeller OR install an engine mounted raw water pump. This drive is the "interim drive" I.E. PRE-Volvo cone-clutch.
Also, if the ignition is electronic and/or EFI , many parts are NLA. so when it quits, you have to go to a carb and/or an after market (marine) dist.
(I sold my 1987 460 dist to a guy that had a 90 460 electronic ign Cobra so he could get it running long enough to sell it!!)
There were also other (smaller engine) Cobras called "King". Some used the newer approx 1995/96 Volvo SX drives but (I think) still used the EFI //Electronic ign systems that parts are scarce for now.....
Bottom line? OMC went out of business around 1998. Volvo Penta continued with the SX line but didn't really continue the Dog-clutch parts supply (there's still many other suppliers of "some" dog-clutch parts including SEI, Sierra, and others....
There's a LOT of boats out there that have Mercruiser engines and drives that are completely supportable at the dealers and in the aftermarket.
If I were looking for a used boat, because for every Volvo powered boat, Mercruiser sells 5, I would look for a Merc powered boat.
But, there's NOTHING wrong with Volvo (unless you get something old because they don't support the really old stuff very well)
Nowadays, I would NOT buy a boat with OMC anywhere in the description. unless it was in perfect running condition, I had a complete Mercruiser engine/drive ready to install, AND had all the OMC stuff sold(with the money in hand) !
YMMV......
Rick
