Overheating?

[johnnyk]

Hello, I took my new to me 23' Imperial with a 350 Volvo/DP290 out for a test cruise and it ran great except after my second full throttle run of no more than two minutes I slowed down to let my son take the helm and he smelled fumes of some sort so we lifted the engine cover and a cloud rolled out of an oily smoke. The engine was idling and I noticed the hose that goes to the water circulating pump was popping ( Like it was under a vacuum conditon). I looked at the temp gauge and it was reading 240 degrees. I felt the exhaust manifolds and they were hotter than before when I had checked them, almost too hot to touch. The temperature started dropping and we slowly proceded back to the dock and everything went back to normal. Prior checks of the manifolds and also the temp gauge readings were good ( exhaust elbows slightly warm and temp gauge reading of 140 degrees) I had replaced my impeller on the pump that sits in front of the engine because several of the blades were damaged. Also, when I took out the drain plugs to drain the block/manifold after a test run in the driveway, there was a lot of sand in the manifolds and the plugs on the side of the block were plugged with sand. After probing with a screwdriver the block drains drained out good. I disconnected the front manifold water inlet hoses and flushed out the manifold to the back to clear those of sand. Any thoughts appreciated. Is it possible the water pick-up at the drive was starving the water pump? Thanks, John