I've got a stock 502 with a Holley 850 on that doesn't seem to run right, been told that's to much carb for the engine, is there a way to "detune" the carb to match up with the engine and does anyone have advice on which way to go with it?

A 850 is NOT "too much carb" for a 502, what it probably IS is the calibration is a total mess, especially if its a "qwick fuel" or proform etc. what brand and model carb?

its a Holley 850cfm double pumper manual choke

so its NOT a brawler or quick fuel, post up the model # if you can

I don't have the exactly numbers for it I will get someone to get them from the boat tomorrow and posted them here

turns out I'm wrong it's a 800cfm
model numbers are
9022
1137

so at least you dont have a chinese proform or qwik fuel. The only real way to get it correct is install a 02 on your boat, get accurate 02 readings thru out rpm band VERSUS vacuum then go after the ares its rich or lean with jetting, air bleeds, fuel passage mods, etc. I do have a mint stock 502 carb off like a 1993 502 mag carbed that is unmolested Id sell fairly reasonble. I would reccomend going thru it with new gaskets, etc as it has set for a while. Where does it NOT run right?

It's sluggish getting going, last half of throttle almost makes no difference feels like it bogs and and dies back

feels down on power also it's a 24 foot speedboat and only getting up to about 55mph

the carb was previously on a 500hp but swapped over to this engine as the 500hp had cracks in the bores

have you checked timing, what advance are you running

timing has been gone through set at 32