Thank you everyone for your replies. You have given me a lot to think about.
Thinking about the Plas Menai little ribs, which are 4.6m? with 40HP four strokes, I think you may be right that 40HP is going to be a bit marginal. I am sure the 55s would do, so perhaps I am looking for 55-75HP ish.
The price points are interesting:
£2.2k complete and working, no parts required - also includes console (which I need) On the other hand I could get a complete rib, engine & trailer package from ebay for this - but the engine might be rubbish in comparison. I don't have the experience to be able to value outboards with any accuracy.
£1k (Beamishken's mate) rough but working and complete (tempting, but haven't even got that right now)
£? Beamishken's 70HP ebay special. No remotes or prop and needs a service kit minimum so add at least £200? £300? All parts seem frighteningly expensive. If it sells for several hundred and things go badly, then I could see this heading to £1k if I value my time at nothing. Am I being overly negative? I wouldn't normally consider a non-runner from ebay as "I haven't tried it" is code for dead as a door-nail and will never run again, but in this case with the provenance...
I am good with fixing bits and I do have a lot of tools, but my experience is all with cars and land rovers, except for servicing our baby 4HP yam, which was easy.
I am not in a hurry and my budget will increase when SWMBO has forgotten how much I have paid for the boat and trailer... My confidence will increase when I have stuck the back of the boat back on. I was more looking for advice on what sort of thing to look for so that I can bargain hunt while I wait.
Is there anything to choose between the makes, or is it just condition, condition, condition at the bottom end of the market? How do the spares prices compare between the main brands?
Only slightly less confused.