I've got an 87 Formula 242 that I'm looking to get another 500 rpms out of my current engine so I can jump up one more prop size. I'm currently spinning a 21 Mirage and would like to spin a 23 Mirage Plus. I'm able to get 6000 rpms out of my current engine which is a 439" BBC that has around 525 hp. I currently am running a Weiand Stealth intake with a holley hp 950 and I'm curious if I switched to a single plane and ran a supersucker spacer if I could realisticly pull the extra rpms that I'm looking for? I'm only getting 62 mph and would really like to get to at least 65-67 mph. I know other guys that are getting 62 mph with a stock 502 mag (415 hp) in the same boat so I'm curious if there is something else I should be looking at, it seems I should be going much faster... As it is I'm getting about 21% prop slip which seems really high for this boat. Most are around 15-16% slip.

I just found an article comparing single vs dual intakes and there was only a 7 hp difference between a RPM air gap and the Vic Jr!

the first thing i would do is try another carburetor,,i think that 950 hp is to big for your motor..i would look for a 800 and try that first..i jetted my 355 in my donzi rich until i gt on the water and then started playing with jet sizes,just from going down 4 jet sizes on the secondaries i picked up 300 rpm's..im running a 750 hp style carb..

Very good point or he could.

Patrick's carbs are usually right on. How was the air fuel on the dyno and what RPM was peak power?

I'm pretty sure the carb is the right size I had prosystems build it for my engine combo. It flows 830 cfm's. The HP numbers are very misleading and do not equal flow. I did have to jet the carb up do to a lean issue that ruined two pistons. I do find it odd that the carb gets ice cold when I'm running the boat which causes a lot of condensation. Is this normal for holleys?

As for the dyno, I never dynoed the engine... Once the season is over I'm going to pull the engine and get the thing dynoed so I really know what I'm dealing with.

The carb is converting a liquid to a gas, which takes heat. That part of the carb which is wet with condensation is sufficiently cooled by that process to drop below the dew point of the air.

Think about how an aerosol can gets cold when you spray its contents.

Thats what I thought but I've never felt any of my carter carbs do this.... Although they were all on stock small blocks and not sucking nearly as much air!

first off your small cu in big block is not a good boat set up, boats need lots of torque, thats why stock 502's run close, while your engine will make the H/P on the dyno you may never see benifits from them in the RPM range that you run in, also spinning outdrives in excess of 6k is going to be a issue at some point. That is a heavy boat for it's size and a high torque engine will perform much better...

Start saving your money for a 4.25 stroke rotating assembly. Guys that want to go fast in boats like yours usually build 540's. To get the most out of your engine, I would use a Victor Jr. Super Sucker made my engine go very lean. I use a 4 hole spacer.Then try more props. Maybe get a 23 Mirage plus labbed. Make sure the hull is straight with no hook. Maybe try a -2 shorty outdrive.