cleanig exhaust manifold?

[losciale1]

Good water flow to the exhaust manifold when hose was removed on 5411 disel, but no initial water out of exhaust when conected. I hate to assume but i fear the exhaust manifold is clogged. I always noticed spurts of exhaust water out the stern almost imediately upon start up, but not lately. I am afraid to let the engine temp rise so fast as it never has before. Any tricks to unclog beside removing from the engine

 

[Big Joe]

Clogged manifold

I recently helped a friend on the dock with the same problem on the same engine. His 5411's manifold was completely clogged. We took off the thermostat cover and put in a very little (a few ounces)of "Rydlyme". This stuff is a biodegradable marine descaler. Because of the clog we could only fit a very little amount of Rydlyme in there. The next day the manifold was opened up enough to run Rydlyme thru the engine. We used a drill motor driven pump to cycle the Rydlyme thru the engine cooling passages. We pumped the descaler for 4 hrs then let it remain in the engine overnight. The next day the engine was running much cooler, never rising above 145 degrees. It had shot up to 200 degrees previously. Water flow increased significantly. I also did my Yanmar YSB12 single and it too got rid of most of the steam I had been experiencing and close to doulbled the waterflow.Regards, Big Joe.