Displacement ?

[spunkyjr]

Exactly what is it. Mercury 8 hp and 9.9 are the same except for the displacement. Price wise the 8hp is about $400 cheaper. Just wondering if the 8hp would be a better buy.

 

[Bifflefan]

Re: Displacement ?

Displacment is the volume of a cylinder (with the piston a Bottom Dead Center) excluding any dish in the cylinder head.
It is measured in CC (cubic centimeters) or CI (cubic inches).

Unless my memory fails me, to get the volume of a cylinder:
3.14 x (Bore x Bore) x Stroke.

As to the 8 or 9.9 hp. go with the bigger one. Its better to have more than you need, than less than you want.

 

[Silvertip]

Re: Displacement ?

The forumula is actually 3.1416 x (square of 1/2 bore) x stroke x number of cylinders. Or another way of saying this is the area of the circle times the stroke. Area of a circle is Pi times the radius squared. Or yet another way, area of a circle times the height of the cylinder. To illustrate this a 350 cubic inch Chevy V8 has a 4 inch bore and a 3.48 inch stroke. Therefore 3.1416 x 4 (the radius squared) x 3.48 = 43.73 cubic inches/cylinder. There are 8 of them so 43.73 x 8 = 349.84 cubic inches. If you want that expressed in Liters there are 61 cubic inches/liter so 349.84/61 = 5.7L (5.735 to be exact but whose counting).