The one that came manual will have a huge coil of spring acting as a counter-weight, which helps you with the lifting. I'd assume the one with motor doesn't have that, and completely rely on the motor to lift the door, so if you were to remove the motor, it will take huge amount of strength to lift, and it won't hold position so it might slam down at you at any given time.

So imo nope, it's dangerous.

Unless you are the Hulk, it is extremely unlikely you’ll be able to open this door with only a handle, like you would a conventional residential garage door.

You can remove the motor, but you’d want to replace it with a manual chain hoist. You’ll want to research “commercial roll up door chain hoist”. I think they are mostly similar, but maybe not all exactly the same… So, make sure you get one that works with your door. There will likely be a bit of customization involved with the installation to get things lined up correctly.

In my experience this is a no-go. These things are very compact and hard to modify. The door will be pretty heavy and you need some kind of ratchet system so you can open it without supporting all the weight manually all the time. And also to prevent it from just rolling back closed again, which can be dangerous if the thing just falls and will probably break the door. It needs to be reversible, so you can close it when you want to, but be braked during the close. To do this, you will probably need to adapt some kind of chain hoist or similar. Maybe one with a mechanical advantage if the door is really heavy, it doesn't look heavy but from a photo it's hard to judge.

You need to pull the thing off the wall, completely disassemble it and then modify it. Which means metal working, cutting, welding etc. On old shitty metal, so skill is required. And you need a hoist to sacrifice for the mechanism to drive it. And you need to be very sure about what you are doing, so it doesn't fall apart or break in use. You do not want to have a door like this slamming down on someone or something, or the whole thing coming free because a weld failed.

What is the problem you are experiencing? Replacing or repairing the electronics and/or motor is probably the easy way. Noise shouldn't be an issue as the mechanical noise would far exceed the noise from any motor and a manual ratchet would be a lot louder.

I was struggling with a similar situation and after repairing the old piece of shit motor for the seventh time, I replaced my roll up door with some pretty swing out doors (I had the room). They are not only insulated, but look way better and have windows in them. I actually ended up selling the old motor and got scrap metal value for the old door, but the new doors were still expensive. Still happy with them to this day.

Obligatory, "don't fuck with garage door motors!" The spring is under tension and people have died messing with them.

Thank you everyone for your very useful comments 👍 Especially the warning about the motor!

The property is in need of repair and was abandoned for a while; I am slowly trying to improve what I can without spending any money (if possible).

The garage door was previously operated by a remote control; when it worked it was intermittent and there is no other exit; I was often worried someone could get trapped in there; especially if there was a power cut. I enquired about a crank, as there is a socket, but this would only work from the inside and the crank would be very slow to operate.

Unfortunately the motor no longer works, I replaced the battery in the remote and tested to be sure. I don't have the money to replace anything, and if I did, I would probably prefer to just buy a manual 'tilting' garage door type.

At the moment the door is up/open, and has been for several years (the photo is old), I am currently using the garage to store wood for now.

I don't think the door is too heavy; I think it would be possible to lift it/modify it. The photos are not so clear but the metal is thin, probably aluminium. Although it would certainly require some effort to lift and would most likely slam down without some support.

If it was safe to remove the motor and easy to lift/support I may have considered some modifications using what I have lying around. But I am thinking given the danger/cost/effort it may stay as it is for now until I have some money to replace it completely with a tilt door.

Thank you all again for your advice, this is a great first experience here.