I agree with the prop reccomendation - call Brett. You should be doing more than that, I'm turning 57 gps any day with my 257 w/ the stock 7.4 300 hp. Water right, 58 is possible.

i think you'd be better off with a mirage...

Well looks like I will be calling Bret @ BBlades. Thanks for the info.

Would their be much gain if I changed out the manifolds and pull the mufflers out of it?

The Gil-designed Merc manifolds that came on your HO actually flow pretty well. Since you have a 2003 boat, the manifolds themselves may be aluminum. The risers are stainless. If you want more noise, by all means change out your existing tips but do not expect any gains in speed.

Given the low X on your drive, my guess is Brett will recommend a worked Mirage Plus for the best top end speed.

Damn Verbi69! I need that motor!!! You interested in a stocker 496ho in trade?

What are the details, year and hours??

If you are interested i have a custom labbed and cupped 3 blade mirage prop in 99 percent perfect condition solid hub, 23 pitch just rebalanced and sharpened. It ran 3 mph faster then my mirage plus.