Poulan pro, right out ofr the box model pr625n21rh3 serial 012010m 004039. the problem is it won't cut the full width of the deck , have to overlap 3" to get full width cut????

Take or call the saw shop and give them your serial # they should be able to tell you the model or take your saw down to the saw shop that sells your brand of saw and ask them. Good luck .

Got a hit on Google using that serial. It appears to be a Poulan Pro 655 if the info in the following post from 2009 is correct.

poulan pro that looks like p65 530 029086

What I have done in several cases is: Go online to the Poulan website/go to manuals/select manual for your model and serial number/Parts list. In the parts list, the option between a 42"/46" deck are shown. In these diagrams it will give you the necessary part numbers for belt and other parts that must be changed to receive the 46 in deck.

Make a drawing of the deck routing and pull the belt off the mower measure the width and length of the belt and order one on line or go to a mower shop with the belt and they can size it to the one you need. Do the same for the drive belt.

The blade only cuts on the outer 4 inches of the blade rotation(diameter). As the mower moves forward, it cuts the full width of the deck. If sprigs of grass are missed or excessive vibration is present, you may have a bent crankshaft. Check and be careful, ejection of the blade hazard exist.

Likely the seat safety switch is malfunctioning.

Normally the model number was under the seat or on the back hitch plate.You might be able to do an ebay search for the tractor to research the model number if you cant find it. Yes the diff can be locked but you would have to take the transaxle apart and weld the axles to the gear carrier. Al ot of trouble and if you did this it would make the tractor very hard to turn,antifreeze in the tires or wheel weights might be a better idea.The serial number would tell you the age of the tractor.Newer serial numbers read like this 030605bxxxxxx. Date is march 06 2005. Older serial numbers read like this 1910Sxxxxxxx one hundred ninety first day of 1990.

A: Is the blade on right?

B: Is the belt on the pulley?

C: Is the blade tight on the spindle?

D: Does the spindle turn freely with the belt off?

I can't think of any other possibilities

Check your tire pressures:
10 psi. for rear tires.
14 psi. for the front.

Note that according to MTD:
Making sharp right hand turns. Twin-blade mower decks are designed with the discharge on the right side and two side-by-side blades. The side-by-side twin blade decks have the left hand blade positioned slightly forward and in front of the right blade. This provides cutting overlap when traveling in a straight line. As a result, the tractor should mainly operated making primarily left hand turns when cutting. During left turns this cutting overlap is maintained. If turning right when, it is possible to negate this overlap and leave an uncut strip.