Wait a minute, my BS meter is pegged out. I've visted Crater Lake several times as early as 1968 and even then, there wasn't any private boats allowed in Crater Lake.
Just to make sure, I've checked the National Park Service web site. I was surprised to find out that you can scuba dive there. You have to hike down to the lake. Any how, here's what I found.
Private boats and rafts are not allowed on the lake. Only interpretive boat tours and research vessels are permitted. Crater Lake is preserved as a scenic and scientific wonder, not as a recreational lake.
A trip to Crater Lake is worthwhile if you're in the area.