Wow that's kinda bizzar.....every boat I've had tends to idle a little faster once warmed up. I wonder if it's a jetting thing? How do your plugs look? Fuel pressure o.k. the whole time?

Hey Steve, does it run rich at idle (can you smell it)? If it runs richer at idle when it's warmed up it may just be too fat...or the float level may just be a tad too high.

One other thing to check is if it pulls fuel from the venturi's while it's idleing, could be two things if this is the case.

One, the float level is too high or a bad power valve (if you gots one)...

Two, the throttle butterflies are partially open and may need to be number drilled to get the idle circuit to work properly, I know I had to drill mine to .010" (I think) to get some adjustability.

On another note, how sure are you of the engine temp?, could be getting some hot spots during a long idle time (even if the gauge says everythings Groovey

Good luck, let us know how things turn out.

GT