Marine grade fan belts vs auto parts store?

[kirkll]

I've been loosing fan belts on my 1990 4.3 Mercruiser too frequently. These things should last for years, and i've broken belts inside of 100 hours for the last few years.
Am i screwing up buying these belts at the auto parts store?

 

[Bt Doctur]

mercruiser gets their belts from the same place auto stores get theirs. Mis-alignment, over tightening are the main causes of belt malfunctions

 

[jimn]

I've been loosing fan belts on my 1990 4.3 Mercruiser too frequently. These things should last for years, and i've broken belts inside of 100 hours for the last few years.
Am i screwing up buying these belts at the auto parts store?

Make sure the pulleys aren't rusted and teh paint/chrome is smooth. If it is, either repaint after making them smooth or replace them.

Do you see lots of black/dark gray dust in the area?