Hi
I purchased a boat in California with a DART 588 that puts out a little over 700hp. When she was in California I am told that she idled in neutral at 700 rpms, but now that she is in N.Y. (Long Island), she idles approx 1100-1200 rpms, obviously to high to shift into gear (Imco states 800 rpm is max). So, is it as easy as lowering idle screw or will it be necessary to change some of the carb jets (Pro-Systems 1200) ? Is this common when bringing an io boat from west coast to east coast?
Am I looking up the wrong tree and sea level elevations is not part of my problem?

Thanks
Frank

Minus waves and time of day for tides, sea level is sea level. So, carbs won't change calibration by an altitude change of +/- 10 ft or so.

Temp/ humidity may be different from the two locations

Anyway, Suffice to say, someone touched the idle system or someone made a play on words to you.

Start out with the basics. Like you mentioned back off on the idle screw and make sure your throttle lever backs off with the screw to confirm its not in a cable adjustment. Set idle mixture screws. Checks front and rear float levels.

Also ck for any vacuum leaks etc or possible bad gasket. Sounds like a lean condition but might just be coincidental. Make sure distributor clamp isn't lose.

Someone blew smoke up your azz. A carbed 588 with a healthy setup, more than likely isn't idling at 700 RPM in NUETRAL. It would fall on its face when you put it in gear.

Using a programmable ignition, like the daytona sensors box, you can lower nuetral idle, and still get an acceptable in gear idle without stalling when put into gear.

The key words in your post "I was told" --------they lied!!!! No way 700rpms in neutral, maybe 850rpms in neutral and 700rpms in gear if dialed in perfectly.

Jetting has nothing to do with idle.

yeap...not buying what you were told..try just backing it down see how it acts, also see where timing is at idle, if the advance still working possible that its rusted up(typical MSD) and stuck advanced and causing the idle to be up..

Yup all the above. I like my timing at 18 btdc at idle or more so it runs strong at idle and doesn't load up. Turn idle screw back make sure throttle cable isn't holding throttle plate open. There is a factory idle stop that can be moved on primary and secondaries if idle screw is backed the stop. If you run more advance at idle make sure your advance curve does not exceed around 32 to 36 degrees total and all in at around 4000 rpm or more. That means with a timing light at bring it up to 4000 briefly 32 to 36 on the damper. It should ramp up slow and stop advancing around 4000. The Thunderbolt ignition has no counter weights in distributor, it searches for best rpm by automatically adjusting timing while engine is under load. If you you have mechanical advance. It needs to be set up properly or you will blow up your engine if you have to much advance. Pete

For your info..I have a 598... best I can get is 850 rpm at idle...that drops to 600 in gear...makes for interesting docking to say the least

I have twin 572 with 237 int and 243 ex duration at. 050 lift. Valve lift. 640 hydraulic roller cam with short travel lifters. Idle 850 in gear 800. You need More advance at idle for large cams. Believe me you will be able to idle around easily with out fouling plugs.