I can suggest the following:
Take it slowly at first. When you see any strange dog, put yourself between your dog and the other dog. Curve your dog away from and past the other dog, speaking to your dog constantly, telling him "good boy, good boy" and rewarding him (as a lure if need be to get him moving) when he moves with you away from the other dog. When you get past the other dog and your dog begins to calm, praise and reward him for his good behavior.
If the dog pulls you to the other dog, turn the opposite direction and walk away. Do NOT let your dog control the walk and take you to where he wants to go.
As the dog becomes accustomed to remaining calm as you curve around other dogs, you can begin to move in closer (less of a curve) as you pass, with the same procedure of rewarding the calm behavior.
When you are at a point where you no longer need to curve away and the dog remains fairly calm, not pulling or showing body language of aggression, you can let him stop and sniff the other dog. However, be sure to put your dog in a sit/stay BEFORE allowing him (releasing him) to sniff the other dog and greet him. Again, continue speaking to your dog, telling him what a good boy he is, etc. The second your dog shows any signs of becoming aggressive, turn and walk swiftly away from the other dog BEFORE the fight starts, if possible. You know your dog and I'm sure you know the signs by now, so you can intervene very quickly and prevent an altercation.
As the dog calms again and is focused on YOU and not the other dog, praise and reward his calming behavior and continue on your walk. Continue this and the dog will understand in time that his aggressive behavior gets him taken away, but if he's not aggressive, he gets to meet, greet, sniff and perhaps play with the other dog, and daddy praises him and gives him treats for his good, non-aggressive behavior.
In other words, associate GOOD things with other dogs (especially other male dogs) and take away something the dog wants (to be aggressive, or to greet, or play with the other dog) when he exhibits improper behavior.
There are many other threads on this subject and, if you use the search button and search words such as "aggression" you'll come up with tons of good information and ideas on how to deal with dog/dog agression, including the great links give above.
Also check out the book section here at BW for many good books which will help you with training and this issue. One in particular you might want to take a look at is "The Dog Listener" by Jan Fennell. Excellent and will be very valuable to you in dealing with this problem.
Goodl luck.