318 TEMPERATURE ISSUES N 1971 WHITCRAFT

Hello all my name is jason and

Hello all my name is jason and I am new to the site and would like to start out by saying Hello to all.

Now the issues I am having is I just bought this twin engine 318 motoryacht and it will start and run great it is 36 foot and will tug a tube all over but my port side motor will go up to 200 sometimes more on a good run and will steam alot out of the exhaust this is running it over 2000 rpm. If i shut it down to 1800 rpm it will cool of some (180) and wont steam?? the other motor runs great and only steams at 2500 rpm and better but i would assume that is normal due to heck cooling it at that rpm faster there will be some water boiling going on. The motor doesnt knock ping or bang both motors are nice sounding. I pulled the exhaust rubber lines and there is water coming out both sides but what is normall flow?? Is ther a way to clean and backflow the system to try to clean it? The manifolds are probably pretty old but i am 2nd owner. Please any advise is appreciated. And one more thing i checked my rubber impeller and it looked fine not busted fins or anything. It is colled from water pulling from river fresh water. thanks again

Also the easiest way to clean

Also the easiest way to clean the manifolds and risers????

"Check the thermostats, see if

"Check the thermostats, see if they are corroded and working correctly. Pull the riser at the top of the engine just above and behind the pump, should be in front of the your carb. They are cheap to replace $12-15, 160 deg settings. Have new gaskets on hand or some hi temp form-a-gasket handy if they stick and rip and ruin...which they will."

I put in brand new thermostats

I put in brand new thermostats and my motor even has the second temp guage on the manifold for backup or failsafe I unplugged them one at a time and they read exactly the same. When i start the motor with the exhaust off it takes like 10 seconds for water to pump out the exhaust then it pumps good. Riser Is this the antifreeze tank??? is there a good method to clean the manifolds and elbos??