Have a mild built 454 in my jet boat , that I’ve never been able to get to run right in the high rpm. At idle it’s around 11 BTC around 3500 it’s at 35BTC but once you get in the higher rpms it keeps advancing and runs like it’s out of time. Is this the reason for locking out the advance? Do I lock it out and time it then use the start retard function on the box to get it to start ? If I do need to lock out the mechanical advance what rpm do a time it at and to what BTC thanks guys .

I think I’m onto something I’m pretty sure I have the wrong springs In the mechanical advance not getting full advance until around 4500 I’ve read on here you need to be a full advance by 2300-3000 mabey changing the springs and re timing would help

You are correct about having the wrong springs. Using the springs, set your advance timing to be all in at the rpm that your boat has come on plane, probably round 3000 rpm. If you have a speed shop locally, see if they have a distributor machine and have it set up correctly. They will be able to set it up for both your initial timing and full advance.

I also have a spring and advance stop kit that came with the distributor

you need to find out what your timing is doing.

shoot the timing at 4000, 4500 etc and then you will know if it is still advancing.  list your spring colors so we can help get yours correct.