[terry4746]

I am troubleshooting the cooling system on a 1983 Merc 150hp. My question: there is a hose coming from the thermostats and this goes to a tee fitting. One end of the tee goes to the telltale and the other appears to go back into the exhaust manifold (I have disconnected it momentarily and exhaust gas comes out but no water). What is the purpose of this?i have a good water stream out tell tale

[profish00]

I would think it cools the exhaust, on my 150 I have water out the prop IE (EXHAUST)The water is picked up through the waterpump brought up through the engin when the t stats open it releases water to the tel tale and prop (EXHAUST)if pressure gets too high before the t stast open the pressure releif valve opens and relieves the pressure in the heads. as well as the pressure reliefe valve supplies water to the exhaust portsNot the prop (EXHAUST)correct me if Im wrong!!!!!!Ive never seen your boat