thnx everybody
tomcat I am agree with russ sr1 about costs/rebuilt etc.

I have no particular reason to argue for the Torque V12, but if you think about the cost to manufacture/rebuild, you have to take into account the hours between rebuilds. In this HP range we are talking about V8s needing valvetrains rebuilt after 50 hours, maybe rings and bearings after 100 hours, cylinder machining and new pistons after ? hours.

Since the extra cylinders allow you to take a much more conservative approach to engine specifications, I would expect a V12 to last as long as a 600 HP 502, say 300-400 hours before it needs anything. Therefore the cost of rebuilding should be much less than an equivalent power V8.

I don't even know how the V12 is priced so it may not be a comparison worth talking about. I do know that I don't care if the Allstar is cheaper for Mercury to manufacture. What good is a lower up front cost if operating and maintenance costs over the product life cycle are much higher?

The real extra cost associated with any of these 900 - 1000 HP engines is the cost of the VI drive needed to reliably harness them. If I was looking at this kind of horsepower in a big boat, I would be tempted to install 3 @ 600 HP - 502s with Bravo drives. Yes, it would be slower, but I would not be rebuilding engines (and the drives are cheap).