Someone correct me if I am wrong but generally retarding timing increases exhast valve temps. With that being said if you have good exhaust valves you may want to back that timing down a tad. Nickerson recommends 29 or 30. The B&M 250 marine installation manual recommends 28 to 30 max. Might start there and see how it runs after you get your boost back.

The chart in the manual list several part numbers of different diameter pulleys. The smallest amount of boost (4 to 5) list one part number with others going 9 to 10 psi. You may want to check the rotors and see if perhaps there is excessive clearance. I would suspect you should see more than 1 pound even with the largest pulley.

Well, we suspect this blower setup was on a much smaller engine..(310hp 454 or something) ..so when you take that setup and install it on my HP500 that has been massaged already..it just doesn't make any boost for it.... I need a B&M part# 155193 3.34" pulley or a 155192 3" pulley ... I would prefur the 3.34" as it should make me a subtle 5-6 psi..but like I said those are older part #'s that get superseeded to the newer stuff...so I may have to replace the shaft...but we will see..

btw, the clearances on my teflon were fine..so no probs there

Thats great info for you with what Bad Dog has experienced on his set up.
Bajapred...You said you worked the 500 a bit? What cam did you use?

I dropped a valve after I bought my 500 so I rebuilt it to a 509..kept the same cam & valve sizes but ported the heads..i guess I am running about 525hp or so...also it has the CMI headers on it now in place of the Gils...this blower should make me close to 700hp with 5-6 psi boost... If anyone has any ideas on finding the older pulleys that I need please let me know...

Give us the cam specs and the compression ratio.....

Well, the cam specs are the same as a stock HP500..the compression should be around 9:1....stock they are 8.75:1 and with the little bigger bore I figure 9:1

BADDOG, do you have an update on your prop? I have the same boat force 235 with a 700hp/572 and run a 4 blade 24 pitch on it. Today it did 70mph on 5500rpm. Do you think a 27 mirage plus would be too much?

I run a 4 blade 26 bravo 1.. you should be able to run a 26 4 blade or a 27 3 blade easy...I still have my knock sensor hooked up..when I am at wide open throttle it is pulling my timing back a little, but I like the safety feature there..I am guessing if I unhooked my Knock sensor I would run around 70mph GPS...now I am right at 65...before I went back to my V8 module I had the V6 module and no knock sensor, I ran 68mph and was not wide open yet..so I know it would do 70 at least...mine actually idles better with my original V8 setup as opposed to the V6 module...my boat is very dock friendly right now...I still need to tune a little on the carbs, but I am reeeaaal close right now......... I know alot of you read about all my problems I had with this blower install..but in a nutshell..my problem was my water pressure..kept blowing my intake manifold gaskets..finally spun a bearing & now I have a brand new engine again!...but I love it!

the HP500 carb cam was a hyd roller, 222/230 110 .576/.598

I have the same boat(89 23'5 force) .I have a n/a 509 with a 24- 4 blade hydromotive. Im doing 69(gps) at 5100