I recently purchased a new Suzuki 2.5 hp 4 stroke OB.
Break in instructions for all Suzuki are:
1). Idle in gear for 15 minutes. (Always idle for 5 minutes before applying higher throttle.)
"Running at high speed without sufficient warmup may cause severe engine dam-age such as piston seizure. Always allow sufficient idling time (5 minutes) for the engine to warm-up before running at high speed". You should avoid running at one constant speed during the break-in peroid--vary the throttle.
2). Then for the first 2 hours no more than half throttle (3,000 RPM), next Hour up to 3/4 throttle ( 4,000 RPM),
3). The next 7 hours you may run up to full throttle for no more than 5minutes.
Running continuously at full throttle for more than 5 minutes at a time during the last 7 hours of break-in operation may cause severe engine damage such as seizure. During the last 7 hours of break in operation, do not operate at wide open throttle for more than 5 minutes at a time.
Honda for the first hour, 15 minutes at trolling speed, then "Running continu:usly at full throttle for more than 5 minutes at a time during the last 7 hours of break-in operation may cause severe engine damage such as seizure. During the last 7 hours of break-in operation, do not operate at wide open throttle for more than 5 minutes at a time."
"Running continuously at full throttle for more than 5 minutes at a time during the last 7 hours of break-in operation may cause severe engine damage such as seizure. During the last 7 hours of break-in operation, do not operate at wide open throttle for more than 5 minutes at a time."
Mercury 90 HP: 1. For the first hour of operation, run the engine at varied throttle settings not exceeding 3500 RPM or at approximately half throttle.
2. For the second hour of operation, run the engine at varied throttle settings up to 4500 RPM or at three-quarter throttle, and during this period of time run it at full throttle for approximately one minute every ten minutes. (The only one advocating full throttle during first 2 hours.)
3. For the next eight hours of operation, avoid continuous operation at wide open throttle for more than 5 minutes at a time.
Yamaha break-in is very similar to Suzuki.
Finding the best cruising RPM/Speed, also requires proper trimming of the boat. Many do not experiment to see what trim gives the best fuel economy and ride at cruising RPM. There are times when the bow needs to be trimmed down when going into chop, or up when going down wind/waves, to give best/safe ride, and compromise on the best fuel efficiency.
I find that there is not just one speed--it depends on conditions.
