Mercruiser 120
New member
Here is the problem. Everytime I'm at 3/4 throttle or above for a few minutes the temp goes way up. Then I slow and idle it goes back down. When it's on the muffs in the driveway with no load and cold water doesn't heat up, but I don't rev it high in the driveway.
So new impeller. Lots of water flow in. I put a new circulating pump on, not the problem, one that came off was just as nice.
So I assumed it was the manifold and/or riser clogged. Just to see I took the hose off the front of the exhaust manifold that dumps in from the thermostat housing and water squirted/bubbled back up the inlet tube(I didn't think that exhaust could get in the water passage).
Put a new manifold on, was so happy, carb back on, put a newer riser on(holds acetone, passages are clear). Took the hose off again that dumps into the exhaust manifold and water is spitting up a couple inches every couple seconds, like to the cycle of the engine.
What is doing this? Is my exhaust pipe that dumps after the riser boot plugged?
So new impeller. Lots of water flow in. I put a new circulating pump on, not the problem, one that came off was just as nice.
So I assumed it was the manifold and/or riser clogged. Just to see I took the hose off the front of the exhaust manifold that dumps in from the thermostat housing and water squirted/bubbled back up the inlet tube(I didn't think that exhaust could get in the water passage).
Put a new manifold on, was so happy, carb back on, put a newer riser on(holds acetone, passages are clear). Took the hose off again that dumps into the exhaust manifold and water is spitting up a couple inches every couple seconds, like to the cycle of the engine.
What is doing this? Is my exhaust pipe that dumps after the riser boot plugged?