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2 stroke verses 4 stroke ?????


rbgraber's Avatar
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07-27-10, 07:43 AM   #1  
2 stroke verses 4 stroke ?????

I had a mercury dealer tell me that a 2 stroke 90 HP is more powerful than a 90 HP 4 stroke. Is that true?

 
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07-27-10, 12:53 PM   #2  
Ninety horsepower is ninety horsepower if rated by the same scale. However, the 4 cycle may have a better torque to horsepower ratio.


Woody


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07-27-10, 01:11 PM   #3  
Typically, the same size engine will have more hp in 2 stroke, but 90 hp is 90 hp

Will they tell you the torque figures? I knew a car salesman who summed it up, "horsepower ratings get people into the showroom but when they drive it, it's the torque which makes the sale."

 
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07-27-10, 01:58 PM   #4  
Thanks for the info.

I will ask what torque is?

Blair

 
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07-28-10, 03:50 AM   #5  
To say that one 90 HP motor has more torque than another 90 HP motor is somewhat misleading without knowing the RPM ranges over which the motors develop their horsepower.

Generally 4-stroke motors develop their rated horsepower at lower RPMs than their 2-stroke counterparts.

Another difference between 2-stroke and 4-stroke: Environmental. 4-strokes don't burn a mixture of gas & oil and tend to burn cleaner.

 
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07-28-10, 01:05 PM   #6  
I agree that these HP ratings are quite misleading.

I just bought a new Mercury 3.5 hp 4 stroke for my canoe.
Had a choice of a 3.5 or a 2.5 hp, the 3.5 being $100.00 more.

I already knew exactly what the difference between the two was but asked the salesman anyway.
He said they put a bigger carb and tuned the 3.5 higher.
1 hp is not a lot of hp but it is a 40% increase over the 2.5.

In reality the engines use the same carb and have the same bore and stroke.
The reason one has a higher hp is that the 2.5 is rated at 5500 rpm and the 3.5 at 6000 rpm!
Pretty clever marketing I think!
What is even more clever is that all Merc engines under 25 hp are made by Tohatsu whose engines are less expensive.


GregH.........HVAC/R Tech

 
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07-29-10, 02:45 AM   #7  
20 years ago we figured the difference between my Merc 170 and my friend's Merc 190: 2bbl carb vs 4bbl carb and his also had heavier lifter springs. Both were 4-bangers.

I could understand the carb, but springs?

 
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