280 Velocity 496 Mag HO bravo 70MPH tub....MPH gain with a speed master?

NONE if your changing from a bravo to a speedmaster set up you would have to add a transmission and move the engine forward,, the hp loss would negate the speed increase,,,, if you want to add a imco or sportmaster lower to your bravo drive ,,,maybe 1-4mph maybe,,,, for the cost and agrivation just add a 2.3whipple for an increase of 15+mph

You would probably need a different prop also...The sportsmaster lower is more efficient at getting water to the prop...which usually loads the prop harder...

This is true with either the IMCO lower or sportsmaster lower.

I would talk to others with the same boat...to find out their set up experiences relating to props...lower units...and outdrive depth...then copy the successful ones.

Chris

+1

You mean a sportmaster lower? I'd lean toward finding a -2" IMCO lower. I think that case is faster compared to the MERC Sportmaster.