hi all,
Im trying to compare a couple of yamaha 4 strokes, both long shaft, both
electric start. the 15 and the 9.9 seem to share a common block, but with a
different carb and prop? they have exactly the same weight (50kg), same
displacement (323cm3), same compression (9.19:1), different gear ration
(2.92 for the 9.9, 2.08 for the 15).

is the 15 just a 9.9 with a different carb? are they just as reliable as the
9.9? Im guessing they wouldnt have as much usable thrust as the 9.9 with
its bigger prop, but probably a higher top speed?

thanks for any and all info,

Shaun

Shaun,
Basically Yes....

The only reason to market a 9.9 is for the "less than 10" market (like
Canada).

Is there any difference in reliability? I very much doubt that it will
ever show up and will very user dependent.

Which you choose is your bet. What are going to do with it? Do you
want to spend the extra money for the 15?

The High Thrust versions are for things that take a great deal of effort
to get going through the water. It is like holding a car in second gear.

If you are going to push a less than 2 ton sloop, you don't even need
the high thrust version (the new Honda HT backs much better than the
standard). I push a 4800# centerboard sloop with the board halfway down
a 6.0k at just over half throttle at about 1/2g/hr with a Honda 9.9. WOT
gets me to 6.2 and empties the tank way faster. A friend bought the new
TH and you can tell the difference just as he cranks up, but his cruise
is at a higher engine speed and his fuel rate is not as good as mine and
on flat water I can be at cruise at the same time.

What do I know? Well apart from being a lifelong waterman, I'm also a
naval architect and a marine engineer (licensed).

Your bet from here.

Matt Colie



Shaun Van Poecke wrote:
hi all,
Im trying to compare a couple of yamaha 4 strokes, both long shaft, both
electric start. the 15 and the 9.9 seem to share a common block, but with a
different carb and prop? they have exactly the same weight (50kg), same
displacement (323cm3), same compression (9.19:1), different gear ration
(2.92 for the 9.9, 2.08 for the 15).

is the 15 just a 9.9 with a different carb? are they just as reliable as the
9.9? Im guessing they wouldnt have as much usable thrust as the 9.9 with
its bigger prop, but probably a higher top speed?

thanks for any and all info,

Shaun



--
target of diversity
victim of affirmative action
refugee from the war on poverty
minimized by political correctness

On Mon, 12 Mar 07, Matt Colie wrote:
I push a 4800# centerboard sloop with the board halfway down
a 6.0k at just over half throttle at about 1/2g/hr with a Honda 9.9. WOT
gets me to 6.2 and empties the tank way faster. A friend bought the new
TH and you can tell the difference just as he cranks up, but his cruise
is at a higher engine speed and his fuel rate is not as good as mine and
on flat water I can be at cruise at the same time.

Just looking at your friend's Honda HT gearcase, can you tell a
difference between it and yours? I'm wondering if the distance between
the prop shaft and the cavitation plate is greater on his HT.... or if
Honda just sticks a larger diameter prop and lower ratio gears on the
same case.

Rick

On Mon, 12 Mar 07, Matt Colie wrote:
I push a 4800# centerboard sloop with the board halfway down
a 6.0k at just over half throttle at about 1/2g/hr with a Honda 9.9. WOT
gets me to 6.2 and empties the tank way faster. A friend bought the new
TH and you can tell the difference just as he cranks up, but his cruise
is at a higher engine speed and his fuel rate is not as good as mine and
on flat water I can be at cruise at the same time.

On Mon, 12 Mar 07, PhantMan wrote:
Just looking at your friend's Honda HT gearcase, can you tell a
difference between it and yours? I'm wondering if the distance between
the prop shaft and the cavitation plate is greater on his HT.... or if
Honda just sticks a larger diameter prop and lower ratio gears on the
same case.

ooookie doke. Getting no response, I finally broke down and called the
dealer to ask my question. He tells me, not only are the lower units
the same, but Honda doesn't even put lower ratio gears it's high
thrust model. The only difference is the prop diameter (9.25" vs 10")
and the decal on the cowling. Who'd a thunk it.

Rick

Rick,
You Missed a line Look below:

lid wrote:
On Mon, 12 Mar 07, Matt Colie wrote:
I push a 4800# centerboard sloop with the board halfway down
a 6.0k at just over half throttle at about 1/2g/hr with a Honda 9.9. WOT
gets me to 6.2 and empties the tank way faster. A friend bought the new
TH and you can tell the difference just as he cranks up, but his cruise
is at a higher engine speed and his fuel rate is not as good as mine and
on flat water I can be at cruise at the same time.

On Mon, 12 Mar 07, PhantMan wrote:
Just looking at your friend's Honda HT gearcase, can you tell a
difference between it and yours? I'm wondering if the distance between
the prop shaft and the cavitation plate is greater on his HT.... or if
Honda just sticks a larger diameter prop and lower ratio gears on the
same case.

ooookie doke. Getting no response, I finally broke down and called the
dealer to ask my question. He tells me, not only are the lower units
the same, but Honda doesn't even put lower ratio gears it's high
thrust model. The only difference is the prop diameter (9.25" vs 10")
and the decal on the cowling. Who'd a thunk it.

Rick
Standard BF model 9.25*8
High Thrust Model 10*6.5

The older TH Hondas had a different gear ratio, I guess they have
decided it wasn't worth their while.

Matt Colie wrote:
Rick,
You Missed a line Look below:

You mean:
"Yamaha apparently does this with gears, Honda does it with
a larger D and smaller pitch on the prop with the same gears
(this year was different two years ago)" ?

Yep, I read it but I guess it just didn't register somehow. Maybe I
still had the old specs in my head... including the XXlong shafts.

The older TH Hondas had a different gear ratio, I guess they have
decided it wasn't worth their while.

Apparently. Who knows what goes into a marketing decision like that.

Rick

On Mon, 12 Mar 07, "Shaun Van Poecke" wrote:
Im guessing they wouldnt have as much usable thrust as the 9.9 with
its bigger prop, but probably a higher top speed?

Shaun, as you can tell from the replies so far, we need to know your
intended use ....
a) pushing a displacement hull
b) pushing a planing hull
c) combination of both "a" & "b"
d) none of the above

Rick

wrote in message
...
On Mon, 12 Mar 07, "Shaun Van Poecke" wrote:
Im guessing they wouldnt have as much usable thrust as the 9.9 with
its bigger prop, but probably a higher top speed?

Shaun, as you can tell from the replies so far, we need to know your
intended use ....
a) pushing a displacement hull
b) pushing a planing hull
c) combination of both "a" & "b"
d) none of the above

Rick

Its intended as the main engine on a thunderbird 26. i am planning to buy
second hand, and have seen more of the 15's come up for sale than 9.9's
which is what i was hoping for. will be used for general harbour docking as
well as motoring longer distances when becalmed.

Shaun

Maybe I'm looking at a different spec sheet or different year model
but.....

On Mon, 12 Mar 07, "Shaun Van Poecke" wrote:
the 15 and the 9.9 seem to share a common block, but with a
different carb and prop? they have exactly the same weight (50kg),

I'm seeing a heavier 15hp than 9.9hp (granted, I'm looking at specs on
short shafts).

same
displacement (323cm3),

I'm seeing 362cc for the 15hp, and 323cc for the 9.9hp

same compression (9.19:1),

9.3:1 for 15hp, and 9.19:1 for 9.9hp

different gear ration
(2.92 for the 9.9, 2.08 for the 15).

Yep

but different RPM ranges. 5000-6000 for 15hp and 4500-5500 for the
9.9hp.

is the 15 just a 9.9 with a different carb?

My guess...... no.

are they just as reliable as the
9.9?

My guess.... yes.

Im guessing they wouldnt have as much usable thrust as the 9.9 with
its bigger prop, but probably a higher top speed?

Depends.... (see my multiple choice post).

thanks for any and all info,

Good questions. Glad you asked.

BTW, here are the spec sheets I'm looking at:
http://www.yamaha-motor.com/outboard...s/4/specs.aspx
http://www.yamaha-motor.com/outboard...s/5/specs.aspx

Rick

interesting how you got a different spec page from what i did... i got mine
from here

http://www.yamaha-motor.com.au/marin...htm?marine.asp

click on protable 4 strokes, and the two models im comparing are the
FT9.9DEL and theF15AEHL. they have the specs i gave before, wondering why
the page you've given me shows different specs?


Shaun

wrote in message
...
Maybe I'm looking at a different spec sheet or different year model
but.....

On Mon, 12 Mar 07, "Shaun Van Poecke" wrote:
the 15 and the 9.9 seem to share a common block, but with a
different carb and prop? they have exactly the same weight (50kg),

I'm seeing a heavier 15hp than 9.9hp (granted, I'm looking at specs on
short shafts).

same

displacement (323cm3),

I'm seeing 362cc for the 15hp, and 323cc for the 9.9hp

same compression (9.19:1),

9.3:1 for 15hp, and 9.19:1 for 9.9hp

different gear ration
(2.92 for the 9.9, 2.08 for the 15).

Yep

but different RPM ranges. 5000-6000 for 15hp and 4500-5500 for the
9.9hp.

is the 15 just a 9.9 with a different carb?

My guess...... no.

are they just as reliable as the
9.9?

My guess.... yes.

Im guessing they wouldnt have as much usable thrust as the 9.9 with
its bigger prop, but probably a higher top speed?

Depends.... (see my multiple choice post).

thanks for any and all info,

Good questions. Glad you asked.

BTW, here are the spec sheets I'm looking at:
http://www.yamaha-motor.com/outboard...s/4/specs.aspx
http://www.yamaha-motor.com/outboard...s/5/specs.aspx

Rick