LAWNMOWER SLOWS DOWN Considerably WHEN BLADE ENGAGED

[JSBIII]

When I put the lawnmower away a couple months ago it was working fine. This is a John Deere with a bagger system. Engine runs great until I engage the blades in preparation of cutting the grass. Seems to slow a little even before starting to mow but when I start to mow it is sluggish. I put mower on ramps and note that the left blade has a gash at both ends of the blade. Could this be why the mower is not performing as it should. The gash is about 1/2 to 3/4 inch long about half an inch in from the end of the blade. I plan on replacing the blade but wonder if this is really the problem. I have no idea how the gashes got into each end of the blade.
Thanks for any help you can give me.

 

[shiftsuper175607]

When I put the lawnmower away a couple months ago it was working fine. This is a John Deere with a bagger system. Engine runs great until I engage the blades in preparation of cutting the grass. Seems to slow a little even before starting to mow but when I start to mow it is sluggish. I put mower on ramps and note that the left blade has a gash at both ends of the blade. Could this be why the mower is not performing as it should. The gash is about 1/2 to 3/4 inch long about half an inch in from the end of the blade. I plan on replacing the blade but wonder if this is really the problem. I have no idea how the gashes got into each end of the blade.
Thanks for any help you can give me.

The only gashes I have seen were where the blades were so worn it went all the way thru the metal.

The metal is thin at the gashes...?

Check for a bad bearing on a spindle or idler pulley, loading down the engine when blades are engaged.