How to Size a Marine Carburetor

Topic: Sizing a Marine Carburetor

Question: How do I know how big of a carburetor to use on my engine?

Response:

Step 1 Calculate Swept Volume
Pi x Bore^2 (in) x Stroke (in) = Swept Volume in^3
Check out the Mercruiser Spec's page link below for dimensions.....Specifications

Step 2 Convert in^3 to ft^3
1 in^3 = .0005787037 ft^3

Step 3 Multiply by # of Cylinders

Step 4  Multiply by Rpm

Step 5 Divide by 2 for 4 Cycle Engines

Example GM 454 Big Block V8
1) (4.25^2 x Pi)/4 = 14.18 in^2 x 4.00 in = 56.74 in^3
2) 56.74 in^3 = .03283 ft^3
3) .03283 ft^3 x 8 = .26264 ft^3 (per engine revolution)
4) .26264 ft^3 x 5000 rpm = 1313 CFM
5) .52528 Ft^3 / 2 = 656 CFM of airflow