My current setup is running a stock 502 BBC with what I believe is a Demon 750 cfm with vaccum secondaries. The boat runs great and I normally do not have any tunning issues, but after reading all of the posts on mechanical secondaries I am debating on swapping out my carb and possibly the intake manifold while I am at it. Maybe and Air Gap and a Holley 750 DP???

What kind of improvements should I expect from this swap? Once dialed in, how easy is it to keep that tune on the carb with mechanical secondaries? Is the 750 DP enough carb for the 502? Any and all information is very appreciated. Thanks guys.

By going to a different intake manifold and swapping out to a different carb, are there any clearance issues I should expect keeping everything under my hatch? Or should that not be a concern in this case?

Haven't really checked the clearance, but i might have about an inch or so... damn that line sounds like a set up 

GT,

Not really sure of the manifold question. The manifold is the stock manifold that comes with the Indymar 502 engine. Hope this helps...

Right now I am spinning an A imp about 4800-4900 RPM's. After doing research, it seems like that is pretty right on to what this combo was meant to do performance wise (w/ Dominator pump). I have added a droop and that improved performance a bit as well.

The closed engine compartment definitely seems "tight". There is absolutely no air flow going in/out except for 2 3" cutouts out the back top part of the transom.

I guess what I am going after is better throttle response at take off and possibly spin a couple more r's.

Thanks once again for the help GT