Decided to not convert stock 502 mag gen V to hp500 specs.
Only looking for 300 to 400rpm increase for the prop that I have
which works great with my boat. Have decided instead to replace stock exhaust with EMI's for silent choice and replace the stock Weber 750 and possibly the spreadbore stock magnum manifold. There is a lot of info out there and any advice or personal experience on this would be appreciated.

Without a cam change, I doubt you will pick up the 300-400 rpms. I did a cam, carb, exhaust, K&N filter, roller rockers and milled the heads on a stock 454 mag and picked up 350+/- rpms.

exhaust, manifold, and carb should give you a noticeable increase in power. spend the extra $150 bones for a cam and lifter set and you should get the performance increase you're after

Thanks Griff and RCM255-

I am looking for more performance but don't want a motor that
is in need of constant adjustment and I am concerned about reversion. The cost of the cam would be great if it was just 150 but doing the cam requires you to pull the engine, open it up, dyno runs, head work and everything else. wanted to keep it simple but it is sounding more like that is not possible.

has anyone done the mods that RCM255 has guggested on a 502 magnum? What gains and approx. costs?

Thanks,
Dave

Sorry im not going to be much help but i had a 502 that we rebuilt into a 540,because of funds or lack of i had to use the stock intake and weber carb along with stock exhaust.What i need to know is how you found out that the weber is a 750 cfm,and are all the webers 750 cfm that were used on 502's.
I am looking into a new exhaust system now any help on which one seems to be working the best between GIL or IMCO not sure which one to go with.

Kenny-
All stock mercruiser carbs on 502's are 750cfm. The older ones are quadrajet and the newer ones are weber. Hope this helps.
Dave