I have a 1990 SeaRay 250DA that I've been restoring. I'm getting close to finishing but not there yet. I've been putting the finishing touches in the engine compartment and decided to go with a closed loop cooling system. I've installed it completely and did a test run on the hose to check for issues. All was good and I didn't see any leaks. Last night I filled up the system with 50/50 antifreeze and distilled water. I let it run, worked the air out and got everything up to temperature at around 170 degrees. Inspecting with a flashlight all around the engine I noticed coolant dripping at the back of the engine and a slow rate. Further inspection revealed that the port cylinder rear head gasket is seeping coolant. Oh well.....looks like the whole top end is coming off again. I guess since I now have 12 to 14 psi in the block with the closed cooling system I have created an avenue for a leak! DANG !!

Good thing you found it now, instead of it being on the first start up at the boat ramp. Just saying, it sucks, but could suck more. You could try some stop leak...... joking. Good luck

it could have been leaking a long time while raw water cooled. river water doesn't smell like antifreeze, you can't possibly run out of coolant and what does leak the bilge pump takes care of just fine. if it leaks INTO the engine that is a whole nother issue...

Might have been your right. Y pipe was leaking due to a corroded hole in it. Moved engine forward just enough to work it out. Replaced with a good used one. Bought the FelPro Maring top end gasket kit and changing both head gaskets this weekend.