Yamaha took a F 150 with 8700 hours on it and compared its performance with a brand new F 150. The time to plane 4.6/4.5 seconds, Top Speed 43.1/43.6 and mileage:4.32/4.57 were little different! The used 150 was one of two on a water taxi, so it had daily service in Charleston S C (salt water). The two engines were compared on a 21 foot run about. That is pretty impressive for 8,700 hours ! a tenth of a second less to plane, top speed 1/2 knot less, and .25 mpg less! I suspect that Honda and Suzuki would fair about the same. So much for "how many hours should I worry about?" But this was an engine run every day--and most likely well serviced!