Hope this does the trick!

Does this mean you have tried other remedies? Has he been neutered? How odd that he still "mounts" anyone!

Vita started spraying and after having the vet test her and say it was behavioural, I started using the Feliway. That is working great for us! I spray it on the places she was marking, and I made a slip for over her collar and spray on that material. We need to keep it up for 30 days, we are just about 15 day into that. She has not sprayed ONCE since I started! And she is more loving than ever!!

I hope that your remedy works as well. It really is a nuisance when they don't want to cohabit nicely.