how much will a stand off box do ?????

[I DIG IT !]

What are they for and how much do the do???? If there so great why dont all proformance boats come with them??? Can you change the X dimension to get more speed with out changing power??? Any body know???

[Kilrtoy]

All depends on the boat, some it is just a waste of money

[I DIG IT !]

Well I only have a 272 baja with a 502mpi. But I didn't know if I could make my power more efficinet??

[BadKachina]

Join Offshoreonly, go the Baja forum, or the general section and post your same question. I would bet it's a waste of money for your boat. You said it yourself, if it worked on all boats, they would all have them.
http://www.offshoreonly.com/forums/showthread.php?t=131779&page=3&highlight=extension+box

[BADBLOWN572]

What are they for and how much do the do???? If there so great why dont all proformance boats come with them??? Can you change the X dimension to get more speed with out changing power??? Any body know???
They can do a lot and they can hurt a lot. Some boats like them and some don't. They often radically effect the handling of the boat. Not only that, you will have to upgrade to 100% full hydraulic steering. You can not use twin ram or assisted steering. They do not work with the system. You also have to plug the holes in the transom. It is going to probably be a $10k-15K bill when you are all done to do it.
You can change the x dimension without changing power. Both Mercury and Imco make 1", 2", & 3" shorter lower units. Good luck finding one that you can try without buying. Those typically are around $3500.00 for just the lower.
I would talk to someone who knows the boat really well and who has gotten the speeds you desire. They can point you in the right direction. :) All of the items listed above are guesses. They could work or they could be a waste of money.