I gunna be running twin carbs on my 250 blowers. Will twin Quick fuel 650 b2 work on each side
Any advise would be great

Thanks Steve.

What size engine, static comp and boost you plan on running. It doesn't seem like t650's are very common on marine SC' like they are on the street

use this chart to help you it's only a guideline, remember the carb is the governor of the supercharger!!
The number you come up with will be the minimum, so I recommend the next size up

RBS is asked how much carburation is required for a supercharged engine? In other words, how big of a carburetor(s) will the engine require to avoid limiting the airflow into the supercharger. This is determined by a formula that takes into consideration the cubic inch displacement of the engine, the maximum RPM at which it will be operated, and the boost at the RPM. Any increase or decrease of these criteria will require a corresponding increase or decrease in carburetor CFM.
To help you determine what size carburetor(s) will be best suited to your application we have provided the chart on the next page. By following the two easy steps outlined you can figure out your own airflow requirement. One word of caution about carburetors before you begin. This chart address airflow only. It is not an indicator of fuel delivery. Insuring that your engine has an adequate supply of fuel to go along with the air you are providing, regardless of the size of carburetor(s) you are using, is the responsibility of the tuner.

CARBURETION REQUIREMENT FOR A SUPERCHARGED ENGINE
To calculate the CFM requirement of your supercharged engine simply follow these two easy step.
STEP 1) From the chart below match the cubic inch and maximum RPM of your engine to find the airflow requirement of a 100% volumetric efficient non-supercharged engine.
STEP 2) Multiply this figure by the number shown in the lower chart that corresponds with your maximum boost.
EXAMPLE: for a 500 cubic inch engine at 7000 RPM with a maximum boost of 10 pounds. 1013 x 1.680 = 1701 CFM ( A pair of 850 CFM or larger carbs would be well suited to the above example)

even with the above guideline, there are still many variables, supercharger size is one, even though the guide shows CFM it doesn't take cam, compression ratio, or exhaust flow into the mix, it also doesn't relate to type of supercharger, roots, screw, etc etc...

Roots blowers are very hard to overcarb. Im running 850s on 468s. Theoretically, i dont need 1700cfm. But, they work great.

I once had a carb linkage issue. I binded up the accelerator pumps when putting my bowls back on after a jet change. The secondaries on one of my 850s, wasnt opening . So, i had basically, a 6 barrel setup on one engine that day. I knew something was wrong , when i was wide open, and one engine was down on boost about 1-2psi, and a couple hundred rpm. Found linkage issue, fixed it, went back out, and back to normal.

I had 1275cfm, but that wasnt enough.

I would go with a pair of 850s , or 950s. The 250 blower, doesnt need to be governed like adk says, its already too small of a blower. You dont wanna have to try smaller pulleys to get the boost, becauase youre starving it for air on the inlet side

agreed Joe... that was what I was getting at... one can never overcarb a blower!!! I was referring to the general fact that the carb is the governor of the blower... not saying that overcarbing is bad.. however without further info on what the lad's combination is, I refrained from recommending a particular size of carb...

You guys get much snow? we got hit bad!!

Al, its been 59 days without measurable snow in chicago. Unheard of. They are talking 60 degrees this weekend!

dude we got hammered!!!

Lucky!! This winter is the worst

Depending on motor size, a single dominator would add simplicity...fuel distribution may suffer