Upgrade small blocks...
 

I would like to get as much power out of my 1999 350magMPI's as possible w/o losing reliability....So where to begin:
I have a valvetrain problem with the port engine so I will have to pull that head for starters....
BTW...It's a 99 Active Thunder 28' w/400hrs on the motors & Bravo drives....Already added new Stainless Marine exhaust systems...got 150-200 more rpms...
Currently spinning 4-blade 14-1/2" x 26" Hydromotives @ 4800rpm's I see 72mph...To get to 80mph I figure I need 400hp each motor.
1. Can this be done (efficiently$$) w/o supercharging? reliability?
2. If I go through the top ends completely & decide to add the Prochargers, what to expect? Reliabilty?
3. Why would the manufacturer say that the hull is not intended for over 80mph? Liability issue? or is it
a handling issue? My Switzer went 81mph w/200hp Merc & not that I recommend it, I felt fairly comfortable (after the learning curve; ie. throttle through the chine-walk @65). This AT hull is exceptionally built; deep, strong, straight lines...why limit it to 80?
4.What can I expect to spend on a sb top end "freshen -up"?
5. Should I consider new cams? New aluminum heads?

I know many will say that the small blocks won't produce enough torque; but I don't want to put BB's in a 28'AT; plus I like the fuel efficiency of these motors....It is such a nice set-up as is; if I can't do any upgrades I'll just fix the valve problem and freshen up both motors and leave stock.

Thanks in advance for ideas...

.....?

stroke 383 or 400 kit, that will give a nice increase in torque good heads so it will breath

400 HP is alot to expect out of 350 cid and ALOT to expect out of the stock short block. Before I tried it, I'd completely go thru the bottomend. You'd most likely be looking at aluminum heads as well much bigger cams- and compression that would require 93 octane. I can't help you on the Merc injection but I'd venture to guess to get to that level, you'll need to go carbureted.

PM Sydways here on the board. he has a relationship with AT and can answer your questions on the hull speed thing.

One thing to keep in mind- these mods won't add value to your boat anywhere near what they're going to cost you. You may want to put honest project cost numbers on paper and compare that with moving into a boat that's more what you want. The market is flooded with bargains.

leave stock motors stock

Nosurprize there!!

What's up Mike?

We did that on our 272 Formula . Made 383's with 425hp went from 54mph to 69.9 on gps. :drink:

Just curious; where do I get these 383 kits & how much $$?

If you have head issues anyway, 1st upgrade to vortec heads, these things are worth 40 hp at lower rpm over what you have now, assuming you have std s/b heads, you have to get matching intake, rockers to make it work, sconnins $ dickey have the complete kit with everything needed, just did one...the prochargers will do wonders and if you keep the boost between 4-5 lbs and the timing at 28 max and no lean condition should work very well and be reliable, have a friend with twin small blocks in a nova III w/ prochargers 4 lbs, runs 85 on radar, and that is not a great hull, Rob

Just put some 502's in it and sell the small blocks.
Reg. 502 ,415-425 HP reliable . Maybe 100 pounds more but alot more tourqe easy fit ,...............done.:eek: