whats the difference between a 8hp&a9.9HP Yamaha outboard

[J Toth]

Ihave a 02 Yamaha 8hp two stroke. The spec. on it<br />and the 9.9hp are the same. What are the differences and can the 8hp be changed to the <br />9.9hp<br /> thanks<br /> John

 

[JB]

Re: whats the difference between a 8hp&a9.9HP Yamaha outboard

Hi, John.<br /><br />Welcome to the board.<br /><br />In '02 the 8hp was different than the 9.9 in displacement, rpm range, compression ratio, and scavenging (The 8 was cross scavenged, the 9.9 a looper).<br /><br />I don't know what other specs you think are the same, but the gear ratio was the same and the charging output was the same.<br /><br />This is from the '02 Yamaha brochure.<br /><br />It doesn't seem a likely candidate for conversion.