As Krystal said, the first thing to look for is a UTI, especially if he used to pee in the box then stopped.
After that is ruled out, or even while you're waiting for test results, additional litterboxes would help. Some cats will not pee where they have pooped, and some will not do either where another cat has already gone.
I'd definately scoop the boxes at least once daily, no matter how many you have. Even with a clumping litter the ammonia smell builds up and can irritate their eyes, especially in warmer weather. If you have less than one per cat, scoop twice a day. I have 10 boxes for 14 cats ( lining the wall in one small room and two in other rooms) and scoop all twice daily.
Jennie, Gary & our kids:
cat colony: Hunter S Tomcat, Archie and Mehitable, Witch, and Calamity Jane, Cuddlebug, Havana, Ghost, Spitfire Liz, Little Bit, Jesse, Moe, Cali, Stardust, Anastasia & Christy, Sally and the 5 boys
dog pack Heinz and Heidi
rip Tiger, Rabbit, Two Stars, Angel,Elaine, Mungo Jerry, Tex and Ijimus. I'll meet y'all at the bridge.