Im not sure but i ***ume th mechanic who is OMC tech.did.maybe we need to explore that avenue.another mech.said that maybe th timing is alittle off ? I have noticed alittle more motor vibration than i thought i would have but its not very noticeable.this motor is on a 389 javelin.my wot rpms are
4800-5000@63mph.gps. with 2 people. seems like th rpms should b alittle higher wouldnt u think? prop is a 24p.raker.