Building a new motor for my circle boat. It's gonna be a 468 bbc. Approximately 13:1 with a set of dart pro 1's. The heads are the super stock pro 1's. Cam is about .710 lift. Would an 850 be enough to feed it?
What do you have right now? I am a "use what you have" kind of guy so if you have an 850 already then I might use it. If you don't have a carb or intake then I would put a 1050 dominator on it and a good single plane intake. A tunnel ram would probably make more power, but then we are talking about buying two "good" carbs and intake and tuning it.
Are you going to compete in competition that has rules regarding carbs?
I'm not an expert on circle boats, so I don't know what kind of power it takes to reach your desired speed, but I'd say you may need all the carb. you can get, within reason.
There are a number of formulas out there and each will tell you what they want you to have. The 327 I built was very happy with the carb that flowed 830 and the 350 that I just finished likes a carb that flows right at 900. Those are both pump gas. With your compression and cubes and decent heads putting a basic holley 850 on would be limiting your combo. Now, that is not to say an 850 would not get you to your target (as I am sure it could) but it would make it easier. So if you don't have a carb or intake I would go with a 1050 Dominator. If you have an 850 and a good single plane I would probably run them. An 850 usually flows over 900 cfm and with a little work at your shop can flow a little more.