Josh, the 174's would basically help you duplicate the 525sc. The cam used is the same as what you have now, and the extra compression ratio of your 420s will crutch the blower some. You know I like 250s but these could work well.

TZ

FWIW - I have 177's with inter-coolers on fresh 454 roller cam engines making just shy of 620hp, the torque is flat, basically off idle and up. I don't think you could squeeze much more out of that combination of parts. Max RPM with my cam is 5400
Just an example of what can be done with little blowers, I would prefer larger ones and not spin so fast but that's what it came with.

8.5:1 decent alum heads, 731 cam, 177 blower..650+, there you go...

ive got 2 sets of these. Ecus, harness, cool fuel, filter head, flame arrestors, throttle body’s , zero hour Teflon stripped 250 blowers and brand new blower shop lower intakes

How easily would these install on my older Mercruiser 420s? I am not too familiar with the 575sci setups but it looks pretty intense. Shoot me a text or give me a ring to discuss. Number listed above. Thanks!

sent you a text

also have a pr , e-mail me if still looking . [email protected]

Make a bigger hole in the hatch Josh!

I had Merc Mag 454's with the 177 superchargers on them. Comp CAM hydraulic cams(Not roller) 850 Holleys. They both made 575 HP on dyno Not bad for turn key totally reliable big blocks. They were in a Cigarette Bullet. Boat ran 80 MPH in flat fresh water. Miss that boat!