alternator tensioning device

[joe_db]

One type sold by our host has a spring, the other type looks like the one my old Toyota uses has a barrel nut that adds tension.
Anyone have either one or insight into which one works better?

[hanleyclifford]

I have been using the one sold by Moyer Marine for years (also known as the "Dutton Device") with excellent results.

[ndutton]

After several years of experience with mine, an unexpected benefit was it alerted me to belt wear. I replaced the belt and the squeal stopped instantly. In the pre-tensioner days I could have (would have?) masked the wear with greater belt tension. That strategy is on a path to more wear, the possibility of alternator/accessory drive bearing damage and belt breakage.