Blades don't disengage

Is the brake system on the deck and working correctly? Are the brake pads still in good shape and adjusted correctly. Are all the belt guards in place and in good condition? Most likely reasons for the deck not to stop. I know part number 53 is connected to the brake system so most of the parts in the brake system would be near that. Roger

Might also look at 148 the tension spring.
It could be unhooked, the idler arm could be stuck in the engaged position, or a bunch of junk on the deck not allowing it to release.

Brake pads are pretty worn. Probably shot.

Belt guards are good/OK.

All the springs are there, but may be too weak?

Idler arm pivot may be at least a part of the problem. I've cleaned that area in the past and shot a bunch of penetrating oil there. Seems to work OK for a few days, then starts all over again.

Frankly, I'm truly amazed this mower works at all. It's my brother in laws', and he's heaped more abuse and neglect on this poor machine than you could comprehend. "Bunch of junk on the deck" ...you have no idea!!!

I'm thinking the idler arm, arm brake and both springs... I'm not located with the mower. Is there one, or two of the arm brakes? Not sure looking at the schematic...Two, just found a kit on E-bay way cheaper than Sears.

Possibly wrong belt (too short). Belt adjustment too tight.
Marvin

is the engagement lever separate from the height lever? That was setup on mower I was given and after doing a lot of work on it at first cutting blades would not disengage and lever would not move all the way to the off position. So since lever was up off safety switch it would not restart. in my case it was wear on the engagement/brake system where a bracket slid past a pin forcing on the brake. The bracket had developed an unevenness and would not slide past the pin. I evened it up with a grinder and it solved the problem . My unit is 20 years old.

Belt is correct. This mower is at least 15 years old, but engagement lever has no relation with the height adjustment. Last time I did "big" work on this mower I reconstructed the engine cowling, replaced two tires, the fuel tank, and installed a bolt that restricted the deck lowering height... B-I-L would always drop to full down position and drag the deck though gravel driveway and over tree roots. Too lazy to lift the deck for any reason.

I can't pull up diagram at work, but if your's is like mine, the idler pulleys are on a flat plate that pivots when engaged. There is a little roller wheel between two plates that kind of lock them in place while engaged. Mine had gotten worn down so they were staying locked in, I had to shut motor down, then reach under deck to dis-engage. I pulled apart, clean real well and actually ground the plate down a little to make it "smoother" and also mad a new little roller from something I had in tool box. Works fine now and I keep lubed.
As I said, can't see pic, but I would inspect all those pivot points on the idler plates to see if they are hanging up. mine is also rod activated, if your's is by cable, inspect all of it also.

Finally got over to the other side of the state... Replaced the (2) blade brake arms, both springs, and the "big plate" that a lot of the parts mount onto. Brake pads were worn into the metal. Problem is better but not solved. I dripped a lot of light machine oil (all I had there) down the blade engage cable...hope that will help after it soaks a week or so. The deck is rusted through in several places and the metal piece that divides the two blades is mostly gone. I still am amazed the mower runs and cut as well as it does!