Agian, welcome to Ribnet!
I'll second Nos' comments. I am now on my second secondhand rib. (and before you get worried the only reason I sold the first one was to get a bigger one!
) On my current engine, I have spent approx. £5 on a new set of spark plugs on an engine of unknown but I know it's going to be high (it's a '79 vintage ands has spent time as a commercial boat followed by time as a sailing club rescue boat) number of hours.
What has cost the money was 2 new anodes, and an almost entirely new tilt lock mechanism. Both suffering extreme corrosion, I suspect because it spent a long time on a mooring and nobody noticed the anodes had all but dissappeared. Various other bits of plastic bushing have / need to be replaced just due to age & wear. The bushing would probably still be like it left the factory had it been hanging on the back of a leisure craft.
My point is that on an outboard it's quite often the "extra" bits that are the problem. A bit like buying a secondhand car because of it's low mileage engine, but half the electic whistles & bells don't work kind of thing.
Hopefully you'll find what you're after. If it's any help there's a couple of places vaguely near you (Upminster & Rayleigh) that have a pile of old dead engines that have kept my "classic" 1971 vintage Evenrude going.