Doggy Door Escape Problem

Hi! We have a dog door going into our backyard for our 104 lbs chocolate lab. It's wonderful! But our male cat loves to go outside, and we can't seem to keep him from using the dog's door. Our backyard is fenced in, but it's an old stockade with gaps in the planks, so he could get out of the yard. We can't afford to replace the dog door with one of those infrareds that keep the cats from using it. We've had to go out hunting for him a time or two and I'm worried he could get into the front yard and get lost or hurt. For the record, he's been neutered. Fortunately, our female has no interest in going outside, which is good since she's tiny. Any inexpensive ideas to either keep him indoors or at least keep him in the backyard without spending a bunch of money that we don't have?

I have to admit that our dog is very happy about having a playmate outside, and it's so cute when you peek out the window and see them rolling in the grass together. But, I'd rather not risk it. I've never had an outdoor cat and I don't want to start now.

Thanks for your help!

Replace the dog door, fix your fence so the cat can use the yard, or just manually let the dog in and out. There's not really any other solutions.

same "problem" here, strangwings summed up my thoughts too...
Cats explore, that is their nature, their huge curiousity can kill them though, he probably won't stay inside the fence unless it is a cat safe special type fence.

Well only choice I see if you don't want the cat outside is to do away with the doggy door for your lab. Let the lab out the normal way. Otherwise you'll have to change the doggy door to one that is electronic.

But the drawback is that the cat STILL can go out with the dog by timing it when it opens - cats can easily go between the dog's legs