My 323 has a 300 hp 454, and I hit 59- 61 on gps,I was looking into getting a 420 hp 454HO from 1800runsnew and was wondering what your opinions on top speed would be ?? I was thinking around 70-72....

I have a 232 with a 454Mag rated at 385. In the summer the fastest I had it on the GPS is 68Mph. I had it out when it was about 60degrees one day and ran 71Mph on the GPS. So in the summer it would probably see between 70 and 72.

Why not go with a supercharger. I think someone on here has put one on a 232. I don't know what they had to modify to get it to fit. But anything can be done.

Hope that helps.

From what I have heard, its not a good idea to put a super charger on a non-mag motor.

If you supercharge a non mag motor, it will basically shred it!

Is the 420 you're getting an older Merc or are you getting something that someone built?

You probably don't want your 232 to go much over 70MPH. My 232 has around 500HP and starts to get pretty light in the rear-end above 70MPH. I can correct the chinewalking a little by dropping the tabs a tad. It actually handles 2-3 foot chop better than flat water at full speed. I am hoping to get 75 MPH out of this boat eventually, but I don't think I would dare go any faster!Cliff

Is that 420 HP at the crank or at the prop? Merc rates their HP numbers at the prop. I think the 385 HP motor earlier mentioned is really around 415 at the crank. I may be incorrect. This is how Merc and boat companies muddy up the water with speed and HP.
Just something to think about.

Brad Perry put a blower on a non mag 454 and from what I've heard had good luck, I don't know what other mods were done, mabye he'll chime in and give up the info

Well,,,, 1800runsnew.com sells the 454 420hp HO for 4,500. My 232 does 60 now so I figure that needing about 10 - 15 hp per mph, 420 should bring me to about 70... But I have to decide if 5 grand is worth 10mph... The g/f/fiancee says go for it,,, she is such a speed freak...

Go for it. In a few seasons she'll be ready for a blower or procharger on the 420. Thats assuming you don't actually marry her.

I would suggest getting it while she is still your gf. Once she is you wife you get to make a lot fewer decisions!