[MHml] Yamaha 9.9 Problems

[Tom Anderson]

Evan wrote:
>The Yamaha 9.9, while seeming to have it's share of problems (probably
>because they are so popular), in unique.

>It has a very low reduction ratio in the lower gear of 2.92:1.  This allows
>it to turn a big 11-3/4" diameter prop at relatively slow RPMs.

>This is great for pushing boats at displacement type speeds.  Most
>outboards use a 2.08:1 gear ratio, turning a smaller prop quickly.  Good
>for fast planing hulls, not so efficient at 7 knots.

>Evan Gatehouse

The hi-thrust Hondas also work very well for displacement hulls. Their 9.9
uses a 2.33 final drive with a 10"x6.75" pitch 4 blade prop giving similar
performance to the Yamahas 7.5" pitch, elephant ear 3 blade spun slightly
slower. Both have relief ports at the front of the prop to keep from running
over the exhaust when in reverse. The Hondas seem to be getting better at
corrosion control which used to be a problem for them. I had a 9.9 Yamaha on
a monohull, I haven't used a 9.9 Honda and I had a 15 Honda on my Gemini
3000 that worked incredibly well. 7 kts in flat water (basically hull speed)
and 5~6 kts going into 15~20 kts of wind and chop. Both motors are expensive
but I don't think you would go wrong with either one.
Hope this helps, Tom