[MHml] Yamaha 9.9 Problems

[Michael Conley]

Hi Philip
      You might want to look at a 70 hp evinrude etec same weight as two 9.9 and it has 25amp charging .
  Mike
Paul Nudd <paulnudd at actionpotential.com.au> wrote:
  Philip Pryor wrote:
> I have just started building an 11.7 Pescott cat in Noosa and got to sail in
> a race on the recently launched sistership. Apart from sailing like the
> wind, (most of the others had a 45 min handicap start on us and we beat the
> next boat home by 25 minutes) the sister ship is powered by twin 20hp
> Honda's with four bladed props. The builder usually puts 9.9 Yamahas on but
> the Honda's have impressed everyone far more than expected. Certainly the
> speed is fine (up to 9 knots) and so far the ability to power into a decent
> headwind/waves seems to be fine with the builder thinking there is less
> cavitation-though this is not fully tested yet. I was so impressed that I
> have decided to go for the Honda's myself as they are the same weight as the
> 9.9's.
--------------------------------------------------
I did a thorough comparison in the mid 90's between yamaha 9.9 and honda 
15 on XL2, published in Multihull World Magazine.
At that time both had 9.9's and 15's which were exactly the same, 9.9 vs 
15 was a marketing exercise and the numbers bore no relation to actual 
HP so the only valid measure of expected performance was/is engine 
capacity (swept volume). The Honda had slightly more swept volume than 
the Yamaha. Then there is the gearing, propellor size/shape etc.
My comparison showed no significant difference. Later models of yamaha 
overtook honda in swept volume, then I think the honda increased again.
Now I am sure that the Honda 20 must have significantly more swept 
volume than the Yamaha 9.9/15 and thus should do the job better, 
assuming suitable gearing and propellor. Same weight too? Sounds too 
good to be true but I'll certainly look into it at replacement time.

However I get 8 knots from XL2 (11.7m cat) with my single Yamaha 9.9.
I would be dissapointed to get only 9 if I replaced it with a single 
Honda 20. I would be interested to hear the max motoring speed of the 
11.7 m Pescott using just one Honda 20.
BTW Mike Shelley had 2 x 9.9 yamahas on his 11.2 m Pescott and he 
changed to a single.
Phil, I suggest you talk to Mike about that, as well as building the 
boat (his was the first 11.2 Whitehaven and Mark helped with the 
building). Last I heard Mike was back in Townsville.
PN
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