I wrote this elsewhere for someone else, but the info fits your situation closely enough. When I get to a computer, I will sit down and write a more indepth article and post it in it's own thread.
The general rule of thumb for how long a puppy can "hold it" is one hour for every month of age (until about 7/8 months). Going by this rule, you can only really expect an 8 week old puppy to be able to go about 2 hours before they have to "go" again.
My first suggestion is going to be: get a crate and use it. To save some money in the long run, you can get one that will fit him as an adult as long as you (make sure it comes with one) use the divider the crate comes with. He should be able to sit, stand, turn around, and lay down, but not have extra room to potty in one end and sleep in the other. The majority of dogs will not eliminate where they sleep (unless forced to). If at any time you are not able to directly supervise him (I.e. overnight), he should be crated.
Take him out to potty every few hours and at minimum once in the middle of the night. Take him out every time he wakes up from a nap, and after eating or playing.
Every time you take him out, take him out on leash. Stand in one spot and say your potty word and don't move until he does. As soon as he goes, throw a huge party. Get super excited, give him a really good treat, play a fun game, and act like him going outside was the best thing that has ever happened. He will quickly learn that going when you say to go super awesome things happen. Do not take the leash off until after he has pottied for a few months. Get him in the habit of going first and playing second.
When he is loose in the house, keep a close eye on him. Keep him in the same room as you, and every time he "wanders off" immediately get his attention and take him out to potty. Puppies potty signals can be subtle. Something as small as sniffing the floor, wandering to a corner, or sitting/standing in an entry way can all be signals he has to go. When a puppy has to go, they have to go now. They physically can't hold it for more than a few moments, so be alert and watch for his signs. If keeping him in the same room as you is proving difficult, tether him to you. Wrap one leash around your waist and attach a second one from you to him.
Never ever "scold" any dog for eliminating in the house (unless they are currently in the process of going, but I will touch on this next), scold yourself for not paying attention. A dog will not understand that you are mad because he pooped on the kitchen floor 2 hours ago. He will think you are mad becauseof what ever he is currently doing (which will completely ruin a good "come" command if he gets punished right after he came to you) and that you apparently freak out over stuff on the floor. If you can't help yourself and you must grumble over a potty accident, next time you clean up the mess (because there will be a next time), put him in his crate or a different room and berate yourself for notseeing his signal, waiting too long, or for your poor choice in cleaner scents. Nothing else will be more effective.
If you catch him "in the act", just say a firm (never loud or "mean" sounding) no and take him directly outside. Do they above mentioned potty command/party routine, then come back in a clean up. Nothing more, nothing less. Never physically punish a dog for eliminating in the house. Doing so will only create more problems.
Remember... it's called an accident for a reason.
By taking him outside on a leash to a designated area, you will greatly reduce the chances of him picking up an illness. Sometimes you have to determine if the benefits of the training out-weigh the risks of exposure. In the case of potty training, it is worth it as long as you are careful. The risk of him catching something in your own yard, 3 feet from you, and only being "exposed" for a few minutes is low. The risk of having a 50# 8 month old dog that only wants to poop on paper in the house if not taught otherwise at a young age, is much higher.
"Violet" UAG1 URO1 UWPS UGWPCH UCD CH AA's Ultra-Violet CD CGC TDI (working), ABIMBS, Multi ARBIMBS, Multi MWP/MWPP, HIT (Agility), 2x Obed Total Dog, 1x WP Total Dog, UKC Super Dog #60, 2010 Weight Pull All Star... and more to come.