I have a 502 mag in a 271 fastech that I have done some minor upgrades to. EMI thunder exhaust & EFI upgrade kit. Does anyone know at what rpm peak hp is made with the 502? I can spin a stock 26 bravo 1 to 5100RPM. Would I be better off trying to spin a 28 at lower rpm to stay closer to the peak hp?

5000 rpm's is peak, top end tourque is around 3500

http://www.goautocenter.com/502_h_o_.htm

The 28 will increase your speed at 3000 rpms. So if your cruise more than run wide open it will increase your efficiency and mileage.

Only way to know is to try a 28.But if you load the boat down with people and gear,getting on plane will be slow with the 28.Actually real slow Borrow a 28 and see.And remember, 271's use left hand props,if you borrow a right hand,just run it in reverse to test,no problem.

Did The Efi Upgrade Kit Help. What Kind Of Kit Was It