Hinda 8hp/9.9hp/15HP - what's real the difference?

[mikehoyt]

They all weigh the same and seem basically to be the same motor. So what is the real difference between them?

Mike

[TrueBlue]

When comparing yamaha 9.9 and 15 hp outboards, I had a similar question, since the 15 was more expensive but of similar displacement. Apparently the difference is in the carburetors, which increase HP and fuel consumption.

[DrB]

of HP differences, what information are you looking for?

DrB

[christyleigh]

Things may have changed in different places but 15 years or so ago when I bought my first 9.9 I was told that in some states or even lake specific the "Under 10hp" rules, limits, or benifits made the 9.9 come into existance basically as a de-tuned 15hp.

[TrueBlue]

DrB,
Although it was badly stated, I understood the OP's question to refer to what differences exist in the engine's design to create different horsepower ratings, if the units appear to share the same engine?

[DrB]

now of what information the OP may be seeking based on your and the other responses.

Thanks.

DrB

[TrueBlue]

Not familiar with Honda, but most likely the 15 HP has a larger diameter cylinder bore as well - affecting engine displacement.

[christyleigh]

Originally Posted by TrueBlue

Not familiar with Honda, but most likely the 15 HP has a larger diameter cylinder bore as well - affecting engine displacement.

I think your first post was more on target with carbs or jetting being the only difference - at least the way it was laid out for me a while back. Mine was a 4 stroke 9.9 Yamaha at the time but all the majors seemed to be doing the same thing to get under the 10hp thing. My dealer (small boat dealer not Yamaha-so nothing in it for him either way) told me he could sell me a 9.9 for 1000 or a 15 for 1500 (something like that) being the same displacement but carbed or jetted differently, and that with the high tourque prop the 9.9 would actually do better. Cubic Inches = tourque (basically - other factors of course) so to push my trailor sailor I would be better off all around ($$ especially) with the 9.9 Lots of vague statements I know..... but it was a while ago and some things may have changed..... but many of the same games are still being played.

[mikehoyt]

OK - so we are starting to get into the meat of this.

An 8, a 9.9 and a 15 all weigh exactly the same so there is no sacrifice in terms of heavier to get more HP - just in money and perhaps in fuel consumption?

From what I have been told these are basically the same engine and therefore I would guess pretty much the same manufacturing costs so in theory could be the same price.

So if they are pretty much the same engine is there really more HP as advertised and to the same degree? What about torque and all the other issues?

I have a 4000 lb disp boat 8.33 beam, 26.67 LOA 23 LWL that currently runs with a Honda BF75 (a 28 year old Honda 4 stk 7.5hp very very similar to the BF100 10HP of the time).

So if the engines are so much the same I would think the 8HP would be fine and then would guess that the 15 would simply have more power for adverse conditions where the hull might not be up to hull speed?

OK - not really one question here but rather than 4 different posts - are these engines really different or just marketted differently? If just the carb what would stop an owner from putting a 15hp carb on the 8 hp engine? Is there any real benefit in my application of the 15 over the 8?

I am actually coming at this post from a backward position. I knew the 9.9 was 115lbs and figured I could make do jest as well with the 8HP but was dismayed that it weight the same.

Food for thought on a friday ...

Mike

[Catalina274me]

Here is the spec from Honda Marine. Just do a google search. Too easy. It looks like the only differance in the 8 and 9.9 outboards is carb and rpm rating, the 15 is of bigger displacement.
8 HP
Type 4-Stroke OHC Twin Cylinders
Displacement 222cc (13.5 cubic ins.)
Bore & Stroke 58 x 42 mm (2.30 x 1.65 inches)
Full Throttle RPM Range 4500-5500 RPM
HP Rating @ Propshaft 8HP @ 5000 RPM
nduction Scavenging SOHC
Valves per Cylinder 2
Fuel Delivery Single Venturi

9.9 HP
Type 4-Stroke OHC Twin Cylinders
Displacement 222 cc (13.5 cubic inches)
Bore & Stroke 58 x 42 mm (2.30 x 1.65 inches)
Full Throttle RPM Range 5000-6000 RPM
HP Rating @ Propshaft 9.9HP @ 5500 RPM
Induction Scavenging SOHC
Valves per Cylinder 2
Fuel Delivery Single Venturi

15 HP
Type 4-Stroke OHC Twin Cylinders
Displacement 350 cc (21.4 cubic inches)
Bore & Stroke 59 x 64 mm (2.30 x 2.51 inches)
Full Throttle RPM Range 4500-5500 RPM
HP Rating @ Propshaft 15HP @ 5000 RPM
Induction Scavenging SOHC
Valves per Cylinder 2
Fuel Delivery Single Venturi