Hello all,
Hope someone can help with this. I have a 1988 Formula 206LS that has an uncommon 350/320HP (Bravo 1 OD) EFI from Mercury Racing. I have had an occasional flooding problem. The engine fires up instantly every time, but once in a while I smell fuel richness at the dock then the motor floods and shuts down. Other times it runs just fine and can't make the problem occur. Parts availability for the EFI is a BIG problem, along with lack of documentation and skilled mechanics.

I have just pulled the EFI and the manifold off am going to replave the intake and put in a carb. I have been told that a Holley 600CFM is the best option. I don't want to lose a lot of performance. Does anyone have any insight on carb size for this set up? THANKS!

The Holley 600 will work well. Just be sure to get the one that is calbrated for marine performance. The standard 600 will take jet and power valve changes to run properly.
I'm running 600's and they run great.
PS want to sell the efi stuff?

Thanks for the feedback Sonic. Will let you know about selling/giving you the EFI. I already promised it to someone, but not sure if they will eventually want it.

BTW, it is the one calibrated for universal marine use 0-80559.

That 80559 is jetted VERY conservatively. For my application I had to change the 2.5 power valve to a 6.5, changed the rear metering plate to a billet metering block with 76 jets, damn- I cant remember what I put in for jets in the front, I think 66. I have to check. I have 320 horse Vortecs with GLM manifolds and Imco risers,thru hull exhaust, and K&N flame arrestors with stub stacks, so I was VERY lean with the stock jetting. Since the carbs came with the motors I did not want to buy new ones, I just used the jetting and PV that Holley uses on the performance calibrated 600, and went up about 2% on the secondary side to make up for the Ethanol in the fuel.
Hope this helps you out.

Sonic, this is the type of info I have been looking for. Thank you!