Anyway, I couldn't find a digital thermo today (and didn't feel like shopping around either), so I made a grapefruit sized matzo ball, let it sit for an hour, then boiled it for an hour or so with a meat thermometer in there (well I didn't want to keep poking the thing and possibly break it apart). It got up to 180 eventually, and probably took an hour to get above 160, so I'd boil smaller ones about an hour too, until I get a better thermometer to tell me otherwise. I couldn't cover the pot though (because the thermometer was sticking up, but I had it mostly in the dough, and had the dough under water the whole time), so it might only take a half hour with golf ball sized matzo balls in that case.
Strangely enough, the dough went up to 190 degrees, sitting in the pot of water after it was turned off, so I guess it soaked up more of the moist heat there. I had it sitting in a minature collander within in the pot, and didn't make it a floater, but the bubbles were giving the collander some buoyancy.
Cutting through this now, it isn't soggy on the inside, and cools down quickly. Maybe I'll actually eat it, since my dog doesn't want any... :emoji_fork_knife_plate: