Dean Gellner in Ohio is probably one of the foremost experts on squeezing power out of the 575 sci.

I would start by swap out the 256 Blower for an 8-71 @ 8psi. also maybe add a healthy roller cam to help out.

The question is: how much do you want to spend? If the boat has 200hrs on it you should change the head gaskets and rebuild the blower. You can only guess how I know. If you do the head gaskets with the motor out of the boat it would be a good time to do a cam change. Even if you dont have 200hrs on the boat, if you turn the boost up the stock head gaskets in that motor are a chance I wouldnt take. If the head gaskets have been replaced and you dont want to pull the motor apart, an intercooler, pulley and fuel adjustable fuel pressure regulator is a good place to start. That is basically teagues kit. If you are limited on hatch space the whipple cooler might fit but it is spendy. The superchiller is priced right but tall and you will get into adding scoops and losing you sun pad. Also modifying your covers. As mentioned earlier, you can upgrade to an 8:71 (which is an 1.5" taller) and pedal your 256 for some good cash...I found a good lightly used 8:71 with a low pro whipple cooler for about $3300 complete with carbs and linkages.

I also support the vote for Dean Gellner...

He did heads, custom rollercam, whipple low-pro intercooler, smaller pulley and custom tuning to hit 775hp on my 575SCi's and the best part is they idle like stock and pull like a rocket all the way to 5600.

Just my two cents.

Recently, when I start my port engine 575sci, the engine idles at around 2200 to 2500 rpm versus the starboard engine idling at roughly 1100 rpm.

After a few minutes the port engine idle slows down to match the starboard engine at 1100 rpm.

Is this a concern? What may be causing this and what to fix?

They idle at 1100rpms????? They should idle at about 750rpms.