Ditto on Ian's post. I've been on this forum since 2008 (I think) and it seems that the 150's have fewer serious issues than most. But as Ian said, maintenance is the key to keeping any outboard running well.
Download the free owner's manual from Honda Marine and familiarize yourself with operating and basic maintenance procedures.
Get the engine's serial number and check with Honda Marine to see what info that have on purchase and warranty repairs. Honda Customer Service Customer Service number is 770-497-6400.
See if the owner uses a particular outboard shop for maintenance and repair, and if so, contact them for a record on that engine. If the owner claims he does his own maintenance, ask for a record of it. If owner gets squirrelly about that, you have your answer.
If the engine is still mounted on a boat that's operational, take the boat out for a test run and observe how it runs through a range of speeds and conditions. Be especially observant of performance in the mid-ranges, say between 3800 to 5000 rpm - that's where a lot of issues show up. Observe the rpm's at wide open throttle. They should be around 5800 +/- 200.
Before purchase, I would recommend that you take the engine to a certified Honda Tech and have them do the following...
Dr. H or HDS readout which will ID any sensors that have been out of spec and will give you hours and usage a various RPM's.
Compression and leak down test. As part of that, check the plugs to make sure you have a good burn on all four cylinders.
Check engine oil and lower unit oil for any sign of metal flakes.
Look for evidence of any major disassembly or repair.
It is unfortunate that your experience with the turkey 130 is tainting your opinion about all Honda outboards. Honda has built and sold a lot of different four-stroke engines over the years, and have a really great reputation for their small engines, auto's, and outboards. The 130 was simply an ill-conceived and badly designed engine.
Good luck on this, and let us know the outcome.