Slowwwly overheating--why ?????

[backwater dawg]

OK---I had the same prob on my old boat (1988 Merc 260 ) temp is great all the time running but slow down to idle and the temp slowwwly rises---on my 88--I took the ball-rod-spring thing and stretched the spring and it worked great-----my 2005 5.7 MPI is having the same prob--what do I do to divert more water at idle to the engine than the exhaust---the motor heated up and the exhast manifolds are cool--I have replaced both impelers and have had the boat pulled to check for water flow and everything is good----any ideas ?????????? thanks Steve

 

[danond]

Re: Slowwwly overheating--why ?????

When you say it slowly rises, what temp does it rise to?

 

[backwater dawg]

Re: Slowwwly overheating--why ?????

It goes from 160 slowwwly up--I give it a little rev up and it cools down then repeats-it goes up enough to set the alarm off--then rev it up a little and it cools down--anything past idle speed it runs normal temp ???????