Does any one have any information on these motors? How they would work for a pleasure boat? How much to maintain? Specifications? Anything else?

Are the 900sc just detuned 1000sc? Lower boost, timing retarded, pump gas vs. race gas.

572 cid tall deck (4.5" X 4.5"), supercharged, twin dominator, solid lifter. A popular combination for big motors, but probably not the most practical for a recreational boater. I dont think Merc has made them in 6 or 7 years.
The 900s are a 540 cid (4.375" X 4.44") tall deck.

Great motors...just don't let your wallet be shy. There is a potential for carpal tunnel syndrome...reachin' fo' that wallet

Thanks for the info.

The merc 1000sc i have seen is a 540 with brodix heads roller cam 1071 twin doms.You can take out the 700 lift roller and put something smaller.You can change boost from 12 to 7.5 lbs.They idle rough with the two circuit carbs.

How reliable were the merc 1000's? does anyone have a spec sheet on them as well?

If you take out the [race] cam and high pressure valve springs to a less aggressive set up these motors are reliable at 7 lbs. of boost for pleasure apps.
What specs do you need?

I did lots of research on all merc blower engines before I built mine, this is what I remember:
1000sc 540cuin big chief heads big root with twin dominator
714 lift solid roller
900sc is a detuned 1000sc brodix heads, smaller solid roller
same blower and carbs
800sc 572 low compression gm heads B&M blower twin 700's
flat tappet cam
600sc same parts as 800 except built from a 502
hope this helps

The 1000 sc has brodix chevy style heads.