The belt on my Murray riding lawn mower slipped off. It is a 15.5 HP 42in. I managed tto get the belt back around the pulleys but the blades will only spin slowly..

Safety and Preparation Serious injury can occur if the engine or mower blades accidentally start while you are working with lawn tractors. To prevent this, drive the Murray lawn tractor onto a flat work surface and disengage the mowing deck cutting blades. Engage the parking brake to keep the mower from moving; chock the wheels with a wooden block or brick. Adjust the mowing deck to the lowest position. Turn off the engine and remove the key from the ignition. While not necessary, you may even wish to disconnect the spark plug wire from the spark plug. Mowing Deck Removal You must remove the mowing deck on a Murray lawn tractor to gain access to the belts. Remove the adjustment rod hairpins, followed by the adjustment rod pins from the front left and right sides of the mowing deck. At the rear on the left and right sides, pull out the retaining hairpins and slide the mowing deck suspension links from the adjuster plates to separate the rear mowing deck from the frame. Remove the blade control rod stud, including the hairpin and washer, from the top of the blade control lever shift linkage at the left rear of the deck. Remove the front hanger rod, including the hairpin and flat washer that hold the rod in place. Loosen the belt guide retaining bolts with a socket wrench and remove the engine stack pulley belt so you can slide the mower deck out from under the tractor Transmission Drive Belt Installation Slide the new transmission drive belt between the engine stack pulley belt guides, over the belt guide plate and under the engine stack pulley. Fit the transmission drive belt around the top engine stack pulley. Push the free end of the transmission drive belt up through the transmission shifter hole in the lawn tractor floorboard. Slip the transmission drive belt loop over the transmission shifter. Pull the transmission drive belt down through the transmission shifter hole. Fit the transmission drive belt around the transmission drive pulley and tighten the transmission drive pulley belt guide retaining bolts to hold it in place. Fit the transmission drive belt flat side around the idler pulley. Slide the idler pulley onto the idler pulley stud while holding the belt in place. Tighten the transmission idler pulley retaining nut with a socket wrench to secure the idler pulley to the idler pulley stud. Mowing Deck Drive Belt Installation Pull back on the right side mowing deck mandrel pulley spring-tensioned belt retainer. Guide the new mowing deck drive belt around the right side mandrel pulley and release the belt retainer. Pull the drive belt spring-tensioned retainer away from the mowing deck idler pulley, guiding the deck drive belt around the idler pulley. Fit the mowing deck drive belt around the left side mandrel pulley and under the rear mowing deck cross link rod between the right and left side mandrel pulley. Slide the mowing deck under the right side lawn tractor frame, reconnecting the deck to the frame in reverse order of removal. Engage and disengage the mower deck while driving the mower to test the belt for proper operation.

try this

Hopefully this is for your deck not 100% sure.

Its actually really easy. First, determine the size of your mower deck. Is it 30" 42" 54" etc. Then, go to a home improvement store like Lowes or The Home Depot (or an online retailer.) Search for a replacement belt for your deck size. Removing the old one is easy. Pry back the retainers on the engine pulley and slip the belt off of the pulley. This should make it very easy to pull off the mower deck. Installation is the opposite of removal. Make sure you note the belt arrangement for proper installation. Good luck!

the cam plate that the tensioner pulley is mounted on that rotates back around to tighten the belt as the cable or rod is engaged is likely rusted and worn, there is a bushing in this pivot that can be removed and cleaned fairly easily with a abrasive wheel or pad and lubricated upon reassembly.

the belt may have slipped off the pulley on the left blade.

Get the model number off the tractor, go to:

www.murray.com

enter the model number and you will find a manual with pictures of how to route the belts along with a lot of other good information

Download the product manual from the Sears website. Murray manufactured these tractors so you can download the manual from the Murray website also. Procedure for replacing the mower deck belt is quite simple. No need to remove the deck. Spring location also on diagrams. Mower deck parts diagram breaks down the whole assembly. Easier way to remove pulleys is using an impact wrench, otherwise hold the blade while removig the nut that holds the pulley in place. Use a heavy glove to hold the blade for safety!

my murray Riding Mower will not move forward or backward

Your drive belt is worn/slipping