Here is a useful site re: marking:
Canine Urine Marking (Indoors)
Neutering does not always stop marking so it's a good idea to discuss things with your vet so you don't have any false expectations. I believe neutering is more effective when done earlier and you mentioned elsewhere that your boy is 3-4? Still, it may reduce the behavior so, again, ask the vet!
My Teddy marks so I have kept him tethered to me and try to keep his anxiety to a minimum since he marks when he feels scared or nervous. Marking is sometimes just behavioral, rather than hormonal, so you could keep a log when you notice him doing it to see if you observe any trends.
Hope this helps!