It's an APC prop (10x6), and tru-turn chrome spinner. The engine is tight to the airframe. I've also had the suggestion that a bearing is going out in the engine, and I should service it. It has had one crash on it that effected the nose, however, that was a long while ago.

The engine is running very rich, although there was a day a year ago that it ran very lean because of a carb screw that vibrated out.

Here is my hypothesis...

The bearing is starting to go out. At low speeds, the engine is not drawing enough fuel to work with a bad bearing, so it vibrates. At high speeds, the engine is pulling more fuel, more oil, and is able to build up enough to handle the problem.

BTW, does anyone know Magnum's website address? I googled them and cannot seem to come up with the proper address.