Good morning, just took boat out Sunday. It ran very strong but no boost showing on gauge new motor 406 sbc with 177 blower/ 850 demon carb. 7" lower pulley 3.50" upper pulley. thinking I need smaller upper pulley. chart with blower kit shows estimated boost to be 4.8 would like to be in the 5 to 6 lb boost range( 8.8 to 1 with iron heads 30 deg max adv. 12 inches vacuum at idle) what size pulley to fall into that range? Thanks for any advice. p.s would I need to change belt length?

I'd double check your boost gauge. You should be making something at that ratio on a 406CI. I spun my 177 just a bit faster and made 5psi on a 460CI big block.

Thanks, maybe China junk gauge? brand new Autometer will check. one thought I teed it off with the boost reference line to the carb could that be giving a false reading? the engine just by the seat of the pants with a given of a familiar prop is even now making the boat a rocket coming on plane etc,mid range was badass did not try to wring out yet.

yep

Update, took boat out last sat. tapped on gauge now show 4.8 at 4100 rpm believe will have the 5-6lbs I was hoping for at 5000 to 5100 rpm

Figured it was the gauge. Probably just was stuck

different flame arresters will change boost way more that you think...been down that road !!

thanks I have a 4x8 spark arrester from eddie marine