New build once again... any help is appreciated

[Cisco398]

This is the first project I am attempting for use in my boat. What I am looking for is feedback on this project. Estimated HP and CR and suggested boost. Any pointers on the best combo for reliability and performance. (I know, some say bigger is better, but it’s not always true ) but since this is going into my boat there aren’t too many gas stations between buoys. What are the pro’s and con’s between the 177 with a single carb vs. the 6-71 with dual carbs? Will the 177 with a 850 be a better choice over the 6-71 with the 650’s?
I started with my 1991 Bravo Mag. 454 4 bolt main block going .030 over for a 489 (maybe .060 for a 496... decisions, decisions!!!). The casting number is 10069286
PARTS 489/496 FORGED ROTATING ASSEMBLY
FORGED STEEL NITRIDED CRANKSHAFT STROKER 4.250"
4340 H-BEAM ROD SET BBC 6.385
KB PREM FORGED PISTON BBC 489 3CC FLAT
AKERLY & CHILDS EXTREME PISTON RING SET 1/16 1/16
3/16 4.310
CLEVITE PERF ROD BEARING, NEW MAIN BEARING SET
Melling M77HV BBC Oil Pump
COMP Cams #2110Big Block Chevy Magnum Timing Set
COMP CAMS XEM 234-244 @ .050 110LC 1 165.00 165.00T
HYD LIFTER SET
PRO-COMP ALUMINUM CYLINDER HEADS
320CC INTAKE RUNNERS, 115CC COMBUSTION CHAMBERS, 2.25 INTAKES
AND 1.880 EXHAUST STAINLESS SWIRL POLISHED VALVES. 1.460 DUAL
VALVE SPRING ASSEMBLY. 1.460" Dual Spring Assembly. Suitable for Mechanical Flat Tappet or Hydraulic Roller Cams up to .650 Lift 140 PSI Closed / 360 PSI @ .500 lift. .400 THICK DECK.
I have a choice of superchargers and carbs. Weiand 177 or 6-71 BDS/GMC BLOWER BIG BLOCK CHEVY with either combination of 2-850 CFM Holley, 2-650 CFM Holley, 1-750 CFM Holley.
I am also planning on the MSD Boost timing master with rev limiter. Anyone use this before that can advise?

[Outlaw]

The only suggestion I have on the exhaust valves is
INCONEL

[Placecraft Dragstar]

You need at least a 8-71 with 2 1050's

[Marty Gras]

Go to a performance boat shop near where you live (registered user land) and buy a motor! You seem to be lost as to how blower motors work and then you also need to figure out what kind of boat this motor is going into, so that you may ask a legitimate question as far as "WTF" you are doing! Bypassing your local performance boat shop will insure that the shop will have a hard time in the off season, and in the end KILL that small business owner! None of the people here who are building boat motors can tell what kind of boat/drive/use you are asking about, so your question is without value. Regroup, rethink, reask! Then maybe someone can acctually help you.(boat brand and size, weight, drive gear ratio, exhaust system, use of boat?) Original speed with the stock original motor and drive?

[jimsplace]

Marty Gras
A little harsh don't you think. The boards are here to learn from and help some if we can.
It would be nice if everyone could afford or even wanted to go to someone else to buy engines. Who would you recommend?
In case you haven't noticed, even the engine builders don't always agree on how to do things. Actually, most of the time they each claim their engines are the best, even though different parts are used. Who is best? Who is most expensive? Are they the same? What's a guy to do?
Lets help if we can. I have received some good information from the boards and I have also received some not so good too. It's a start though.
OK, we probably do need a little more information. Type of boat and how it will be used would be a good start.

[Outlaw]

Go to a performance boat shop near where you live (registered user land) and buy a motor! You seem to be lost as to how blower motors work and then you also need to figure out what kind of boat this motor is going into, so that you may ask a legitimate question as far as "WTF" you are doing! Bypassing your local performance boat shop will insure that the shop will have a hard time in the off season, and in the end KILL that small business owner! None of the people here who are building boat motors can tell what kind of boat/drive/use you are asking about, so your question is without value. Regroup, rethink, reask! Then maybe someone can acctually help you.(boat brand and size, weight, drive gear ratio, exhaust system, use of boat?) Original speed with the stock original motor and drive?
Don't mind him Cisco, he kicked his dog when he got registered user land (home):D

[Cisco398]

My father always said "the emptiest drum will make the loudest noise!!" If I had the knowledge many of you acquired thru the years then there would not be a post from me wanting to learn HOW to build my own engine. With that being said, I looked into the valves suggested and still have time to order them. I also may have a good lead on someone that is willing to swap some parts I have for an 8-71. That is if it in the shape he claims. As for my boat, its a 25' Webbcraft Velota about 6000lbs. Originally it had a 7.4 Bravo Mag with a Bravo One drive. I upgraded to an XR drive and wanted to get a little more out of her. I have learned alot since starting this and see there is alot more to look at in building a motor such as this. Again guys, I really appreciate the tips and look forward to get this going. My block is due back in a few weeks and if all goes well I can get started soon afterwards.

[BrendellaJet]

Cisco,
A good place to start would be to define what you want the boat to do well. Some questions to start:
How fast do you want it to go?
What gears are in the drive?
What are the boats capabilities?
What is the budget for this project?
Do you want to build it or pay to have it done?
The old adage-horsepower costs money, how fast can you afford to go? rings loud and clear when talking boat motors. I'll give you some pointers that I learned when undertaking my project.
Dont be afraid to pay a pro to build it.
It always costs more than you first thought.
Set a plan and stick to it. Changing things half way through leads to more expense and potential for more problems.

[ck7684]

FYI, Manley Extreme Duty exhaust valves are Inconel superalloy valves...they run about $40 each...