Hello all - hope you are having a good summer.

Looking to repower this fall and could use some recommendations:

What I am replacing:
Merc 454 330hp carbed closed cooled - one rotates each way
Borg warner 72s
Gill exhausts
4 foot run from Gill to transom with decent slope

What I have to work with:
Pair of 2006 496 long blocks with intakes/injectors/wiring harnesses/stock EFI computers
Pair of ZF63A gears

Goals:
Torque - boat is 15,000 pound deep vee (no steps) 42 foot cruiser with arneson drives
Engines are inboards - little to no room for blowers on top and want to go NA for simplicity
NOT a poker run project - just want to cruise and be reliable - buddy has 550hp 502s and cruises at 38knots, tops at 50 - good enough!

Assume:
Fuel will be non-ethanol 91 octane marina gas
Will be adding over-sized oil coolers
Will remain closed cooling
Open to suggestion on retune existing EFI, replace with newer generation of self tuning EFIs, or go carb - best options? I am a computer geek but not an EFI expert.

Working slob so looking for best torque for the dollar .... reuse everything I can and if possible avoid AFR costs if I can.

Thanks!

No words of wisdom .... huh?

I was thinking the following:

Forged pistons to get to 10:1
Some head work - inconels, springs or find less expensive alternative to AFRs
CAM like the 741 or 731
Swap intake to something like the new Victor Junior and plop dominator 850-1000 cfm
or
Get stock intake ported and get MEFI4
or
Go Victor jr with new generation of self learning EFI "Carbs"
Add pair of monster oil coolers
Raylar stainless rocket set on stock heads

Thoughts?

Dart makes performance upgrades for the 496 8.1. And if the efi system goes down that have parts for a carb conversion. I would call them and see what they recommend for your budget.

Personally the 8.1 isn't my favorite engine, however it can be made to live in the 500hp range, and there is nobody better than Raylar to accomplish this. After calling Raylar I would seriously consider investing in a Holley HP setup. Do the math as it's not cheap.

Thanks Guys - I have checked out the Raylar site and traded emails with them - super guys - very up front etc. but a bit out of my price range at this time. Perhaps I can do some lower raylar stage and get enough torque for my needs ... and move up later.

Guess I'm looking to do things for a bit less cash as I am not a poker run guy and wont be spinning these engines at 5500rpms all day long. This is a cruiser so most of it's time will be at 3800-4400 rpm with occasional blasts to 5,000 to clean out the carbon.

maybe upgrade the EFI and, small CAM upgrade, head clean up and hope for the best?

Hey Swampy (it's CFM) did you you see these just put up on the block ?

http://www.offshoreonly.com/forums/s...take-outs.html

yeah I did but already committed to 496s.

There is far more available, performance wise, for the 454 than the 496. I would sell the 496's and build up the 454's.