1983 Yamaha 30EN Outboards Service Manual, Page 52Get this manual
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POWER HEAD OVERHAUL DESC IPTION The pOWl-'r head is made up of in-line twin cylindprc;, ""hose bore and stroke is 72 mm (2.83 In) and 61 mm (2.4 in)The total pistofl displacement is 496 cc (30.3 c.in)