What causes a serpintine belt to split?
 

I was running through the rough water yesterday and I noticed a little reduction in power. The next time I had the hatch open I noticed the blower belt (procharger) was now 6 grooves not the 12 groove belt and the other half was in the bilge! If the belt is loose will it jump the pulleys?

I don't know if the tensioners are any different in marine applications or not, but my car would do that if the belt stretched. I ran Napa belts and changed them quite often, that seemed to cure the problem. I know they are not cheap, but I have a ton of spares and no more shredded belts!

On another note, I would check all of your pulleys and make sure they are all in good working order.