15 hp and 9.9hp same displacement?

[mays]

I have been shopping around for new motors and notice that many of the 15 hp and 9.9 hp offered by the same company have the same specs (displacement, gear ratio, etc.). What accounts for the difference in power from these similar engines?

 

[pwiseman]

Re: 15 hp and 9.9hp same displacement?

Look at RPMs on the spec. You should see that the higher HP will have higher RPMs. The smaller ones are detuned to limit RPM.

 

[umblecumbuz]

Re: 15 hp and 9.9hp same displacement?

As Paul says...<br /><br />If you're talking carburetor motors, you'll often find that a carb with smaller jets, and smaller throat is fitted to the lower hp motor. Sometimes the exhaust tube is different also.<br /><br />Many 9.9's can be converted to 15.

 

[mays]

Re: 15 hp and 9.9hp same displacement?

Does that mean that you can expect longer life from the 9.9, because it does not have to work as hard?

 

[Navigator]

Re: 15 hp and 9.9hp same displacement?

Dont always assume that the same displacement means the same engine internally. Honda for example, has the same bore/stroke on their 40 and 50 hp outboards. However, the 50 has larger valves, a different cam shaft and changes to the carbs. On first glance, they look the same, but when you get down to it, they are both different. <br /><br />If you are looking to pick up the lesser and modify it to get the higher HP, you'll most likely find that it is cheaper to get the larger one initially.<br /><br />Nav

 

[Solittle]

Re: 15 hp and 9.9hp same displacement?

The life expectancy of these motors is more a function of the proper set-up and service than how hard they have to work. You can read thousands of posts here about engines that are used regularly and are 40+ years old. I don't know if that will hold true 40 years from now due to the extensive use of sensors and computers in the current engines.

 

[Silvertip]

Re: 15 hp and 9.9hp same displacement?

On two-strokes, port size and height are also often altered to achieve higher horsepower and RPM ranges. Just like in cars, cam, compression, carburetion (or FI) are altered to achieve different horsepower ratings from engines of the same displacement. It's inexpensive to do this at the factory, but generally very expensive to do it after manufacture.