i wouldnt trust the hour meter on a used boat. you can unplug them easily then plug back in when time to sell. i would highly recommend a compression test done by a certified master mechanic before purchasing.

400 or less but nothing under 100 would be my suggestion.

I bought mine when it was 15 yrs old. It had 42 hours on it.

That’s good and bad. I had to spend a few hundred fixing fuel related stuff. I’m still chasing a small fuel gremlin. The boat looked showroom new when I bought it and has cost me a couple thousand in repairing seats and now carpet due to accelerated wear.

I’d recommend buying a newer boat, that has logged more hours, than a boat that sat for 15 yrs... it costs about the same.

According to the Yamaha dealer techs that I have been around the last few years, the absolute worst thing you can do to a Yamaha SHO is spend extended time idling at low rpm's. To the point that I had one dealer tell me Yamaha would deny warranty if the idle hours got to high. I have since been told by one of the regional reps that this is completely false. I do lots of offshore fishing so if a boat can't have idle time, it is absolutely worthless to me. Just be aware that high idle time is often sold as a positive when in reality it may be a negative on these newer 4 strokes. All of these relatively new motors can be hooked up to a computer and give you all kinds of data. I would definitely go get that done before you buy a boat.

With all that said my SHO has 500 hours on it now with relatively few problems. From the saltwater guys that run them every day most seem to get about 1000-1200 hours out of an SHO before some major issues pop up. The old grey f series Yamaha can easily get 1500-2000 hours when maintained properly and used regularly. Thus the reason you see very few SHO's in saltwater anymore.

I can't speak to Mercury longevity because I have not owned one in over 20 years.