The rolling idle is not normal, even if the manual says so. I'll bet it's a sticky throttle cable. I'd like to replace my throttle cable, it's been sticky since new. I lubed it with some graphite cable lube that I bought at the local Harley dealer, that helped. When the idle is high, try opening the clamshell and pushing the throttle mechanism where the cable attaches forward, see if it moves a tiny bit, dropping the idle. Be careful and make sure the boat is in neutral.
I know that the throttles on the V drives and on the 21 ft boats have nice smooth action, but the 22 ft D drives have a different cable routing. I'd like to find out if I am the only one with this problem or if it is common to this model. I didn't realize how screwed up mine is until I drove a couple of other Toyotas. My throttle action has been stiff since day one. It doesn't matter that much to me, it actually makes it easier to drive with PP if the throttle is a little stiff.