I have a 1989 Mercruiser 350 260hp that is running hot. The engine was just replaced with a reman. unit. It has a raw water cooling sytem as pictured at http://www.mercruiserparts.com/images/cruiser/816596/21.png . I ran the engie in the driveway with muffs and it felt warm but temp gauge read ok. I put the boat in the river and the gauge read ok but the risers and manifolds were so hot that you couldn't get near them. I am assuming they should be touchable. I installed a new water pump in the lower unit. After I got the boat home I replaced the hose in the gimbel housing and restarted it on the trailer. Still the risers and manifolds quickly heated up. I pulled the hose on the port riser to see if and water was coming out. I only had a little mist coming from the riser. I also pulled the hose coming in from the transom and water was present. I them pulled the therm. cover and could see water in the intake and the therm. was open. (new 140 therm) I may have a problem with the gauge but the engine feels ok to the touch but the manifolds and risers are hooooottttt I have rarely heard of a circulating pump that doesnt pump, usually has a seal or bearing go in it. I am new to the inboard/outboard scene and need help. The original engine only had 6 hrs on it before it had a water down the intake problem so the manifolds appear to be next to new. The gaskets between the riser and manifold were replaced with the one listed for it. Had long slots on two sides and little holes on the other two.
