Difference between High-Thrust and normal Four strokes

[joblo33]

I have a 1986 and a 1989 Yamaha 9.9 High Thrust Four Strokes. I was wondering if all I have to do to convert one to a normal engine for my 12' would be change the prop to something like a 12 pitch. Are there other differences (leg, ratios, rpm range...) Would one of these years be better to convert than the other?<br />Thanks,<br />Eric

 

[ivar]

Re: Difference between High-Thrust and normal Four strokes

not sure on the 9.9, but the high-thrust 50HP has a different lower unit with lower gearing and a prop with larger diameter to give better thrust at lower speeds. <br />If I remember right , the 9.9 HT also is tuned to give max power at a lower rpm.

 

[joblo33]

Re: Difference between High-Thrust and normal Four strokes

k, thanks.<br />I think I'll just sell these two and buy a newer non high thrust 9.9 four stroke.<br />Eric