Have Boat Questions? Ask a Boat Repair Expert.
Hi and thank you for your question. Typically when you don't see the spray out the tell tale fitting on the side of the boat, it means you have a clog in the cooling system somewhere. I suggest following the flush hose down the hose and finding the Y where the flush hose meets up with the cooling line from the jet pump.
Once you separate the hose coming from the back from the y, blow through it backwards, from the engine compartment towards the stern. If it does not blow through easily, you have found your restriction and the reason the tell tale hole isn't working.
Just on the off chance some industrious critter built a home in that very line, designed to let cooling water out so the operator can see it, you can straighten out a wire coat hanger and use it as a deep probe to poke it in the outlet and make sure there are no critters gumming up the works, or critters nests too.