When doing three cylinder engines like OMC 50 cu or SST60 type engine be carfull of the engine vibration at 4000 rpms. We avoid that rpm.
run 3500 at 3/4 throttle
1 minute idle
3500 at WOT
1 minute idle
4800 at 3/4 thottle
1 minute idle
4800 at WOT
Do no run at the vibration points, parts will shake right off the engine.