blower motor timing

[wfoflat]

I put a blower on my boat and have been told by many people to lock out my distributor. Why is it not good to run an advance? If I lock the distributor at 28deg or have the total advance at 28deg what would the difference be?
THANKS FOR ANY HELP
IM JUST TRYING TO MAKE SENSE OF IT

[wfoflat]

The boat is a 1972 sanger bubbledeck flat.The motor is a 402 bbc with stock oval port heads and a solid cam with some lope to it. the blower is a 177 weiand. distributor is an msd pro billet with a 6al box. compresson is a guess of 9 or 10 to one. I know the compression is high for a blower thats why im trying to play it safe with the timing and running good race fuel. The boat also has a 100 shot of nos but I dont plan to use it. I have been recomended to run an rb prop around 11.25 or 11.5 by 15. I dont know what gears are in the casele box. When I was running a tunnel ram with a single 750 demon and a 3 blade brass prop 12 by 14 I got a gps of 70 mph. I would like to see this boat do at least 80mph. The motor tachs 5700 rpm with the 12by14 3 blade also tachs about 5700 rpm with a menkens 11 by 16 two blade.
Thanks for the help