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Message: <blockquote data-quote="rotus623" data-source="post: 432213" data-attributes="member: 15266">Yes! Displacement will make an absolute difference!! Most of the OMC 90's are actually de-tuned 115-130hp engines.   Engine manufacturers only make a certain number of block sizes and then have 3 or more hp rated Engines for that particular block size. Remember the old saying, no replacement for displacement? Hp is just a number. If you take a Mercury 84.6 cu in 70 hp and put it besides a Yamaha 51.8 cu in 70hp, the merc will completely blow it away!! HP is just an equation of torque and rpms. If you look at a dyno curve, the peak hp is made at the engines upper rpm limit. The torque actually starts to fall of before the peak hp is hit. Big blocks make their torque early. That's why we use big motors to get big loads moving.So take that "all x hp engines are created equal" out of your head and get you the biggest displacement blockthat you can fit on that HP tag!! I'd be right there with ya but I do a lot of idling and slow anchoring so I really enjoy the 4 stroke for that.</blockquote>