I'm researching repower options and a little conflicted on shaft rating. I have 2.5" Aquamet 22 shafts. I was previously under the impression they were good for up to 1,450 hp. I used the shaft calculator on boatdiesel and with a safety factor of 2 it suggests I'm OK up to 2,000+ hp. Is a safety factor of 2 enough? if I go to a safety factor of 3 it drops to just under 1400 hp rating. Seems like a factor of 2 is enough? I'm looking at engines in the 1400 - 1600 hp range. So even with a safety factor of 2 I would be conservatively under max allowable. Am I looking at this wrong? Side note: I pulled shafts two seasons ago and did a TIR and full NDE and there were no indications of any issues.