I am running a 92 389T with a 91 evinrude 150. I am running a 24 pitch renegade (was 25, croxton pitched it down and added more cup) on a 5.5" jackplate, about 3.5 under pad. I am turning it 5400 and will run about 58 or 59 in warm weather. I still think i can squeeze 61 out of it with more set up time as i am still going up with the prop. Just waiting on better weather.I am not an expert but i would think you could get 64-65 out of your boat.
I have also read that our javelins like tempest props, I recently purchased a 25 pitch tempest to try also.
Hope this helps.
92 Javelin 389T , 91 Evinrude Intruder 150
150 Faststrike