boost question
 

Just wondering what boost you guys are seeing on a 509 w/m3 procharger and a 4.25" pulley at 5200 rpm. Thanks in advance Trevor

4-6 psi,probably6 psi if your at sea level,Smitty

Smitty, I took my boat out for the first time yesterday and I was seeing 5# at 3800 6# at 4000 7# at 4200 8# at 4500 this was after testing, but the first run with a quick stab after I was on plane she was at around 10# at 5200 with some prop blow out.I would say it was the gauge but I slipped a boot on the cooler line.On the dyno it ran 7.2# at 5800 but he wasn't loading the motor real hard above 4800 rpm. I just did a search on pullies and it looks like my lower is around 7.75"? it is tight down there to measure. Any thoughts the motor is a hp500 efi with stock heads? Thanks in advance Trevor

I'll have to measure my lower but when I was still running a 502 with my m-3sc and had 8 rib drive I started out with a 4.25 pulley on top,went to a 4.0 then a 3.85. I have since swithced to 12 rib drive,the lower pulley is same dia as old on but wider and a 3.85 gives me 10 psi at 5900 on my 540,3.70 gives me 12 psi at 6000. I'm at 600 feet above sea level which is negliglble. I never saw over 6 psi at 5200 with the 4.25 at 5200 on mt 502 but my lower pulley might be 8.5" though,Smitty