Cat poo question

Ok I never thought I'd need to ask any thing like this but here goes. Our 17 year old winky (male fixed) seems to be having a problem he has always had a herd feces but lately It's like it's been on the desert for days and it's only mintues old . It is very smelly too. (Please no klam juice suggestions) He has free access to water has free feed to kibble gats 1/2 can of moist canned food. Nothing has changed diet wise same foods as always.
Any ideas?

Has he had blood work done recently? Constipation can be a sign of something worse (especially at 17 years of age). If he gets a clean bill of health from the vet them maybe some cat-lax might help soften things up.