I'm not clear on why you would buy a GCV160, one of the few really unattractive engines Honda has built, but I guess that is your business. The main issue is how long the engine has had water in it. Obviously stripping the engine and cleaning it out is not all that expensive or time-consuming, but if there is corrosion of the innards, the job gets larger and more expensive. Slight corrosion of the bore can be recovered, but if it involves the valve guides or the crankshaft, it becomes more troublesome. I once rebuilt an engine that had been full of water for about 5 years, but that was a twin cylinder Lister diesel, so at least I had something useful at the end of the process.
Spare Honda vertical-crankshaft engines are not scarce, but in my experience they are nearly always ex-contractor engines that are in need of new rings and some other tidying up.
