Yes I have for my friend with a single engine Checkmate, Had to pull a total of six jet sizes out to clean it up, 2 from the primaries, 4 from the secondaries. and leaned out the secondary high speed jets 2 sizes. Now my friend may not have givin them incorrrect info to begin with? don't know. You won't burn pistons thats for sure! you might wash down the cyls though! Not bashing them this was my one time instance with them. may have been a fluke!

Yup, Holley has one and some aftermarket tuners / holley aftmkt parts manufacturers make some.

Many look like this:
http://ep.yimg.com/ay/spideraccessor...-470-cfm-1.gif

when comes to jetting the booster venturies change it as well, they have a few different ones now and the way the air signals the carb can be way different so jetting for the same CFM carb may be way different.

What about when the secondaries open, my holley secondaries start opening just off idle. One 850cfm on top of a 177 blower. Not like the linkage shown above.

I have a 99 388 Slingshot with 500HP's in it. Only had it a short time, first time with a carb boat so it is a little Greek to me but along the lines of carbs the factory 800's that were on it were in need of rebuild bad. I was going to send them to Nickerson but had a buddy talk me in to letting another guy build me a set of 850's for it. Idles like a dream, smooth on power but feels maybe down on power? 76-77 MPH48-4900 RPM, 1.5 gears and stock 30's. Best I have seen is 80 with the old set up (when it would run). Compared to another friend who had the same set up and was seeing 5200 RPM with the stock set up and 82-83 MPH. I figured I'd have more power? More air/more fuel ='s more power? Trying to keep from doing anything else drastic to these motors as I want to re-power maybe next summer but it has been frustrating.

Stay with the factory carbs on the HP500's. No reason to change.

Yeh, that's coming from a 'Stock Sucks' kind of guy...but, it's not like the HP500 is OEM per say.

has a 1-1 linkage, not a good setup on a boat...

Hard to compare two carbs, without a dyno, or some air fuel ratio numbers. Bolting on a bigger carb, that may be set up too rich, or too lean, can hurt power. Not because the CFM of the carb, but because the calibration may be off.

Thanks. Guy that built the carbs test drove the boat with the tech down in Clear Lake, TX. and adjusted it out, did whatever he does etc. Idles like a dream, power is smooth and crisp, great docking manors etc...but just feel like the top end isn't there. I am following the thread you started MILD THUNDER, thanks for the info!

To be more exact: More air with the correct amt of corresponding fuel = More power.