How to find obstruction in cooling system

[sebas54]

Hi, I have a 4.3l merc. I/O alpha 1 raw water cooled.


When i run at hi rpms the temp. will slowly rise to 170 and then I pull back and let it cool. I think that there may be an obstruction somewhere but don't know how I could tell without taking everything apart. One riser gets hotter than the other but how can I tell if it an obstruction from the inlet or outlet of water.


Thamk you.

 

[slasmith1]

Re: How to find obstruction in cooling system

you answered your own question. you need to take it apart peice by piece and check it I would start with the manifold/riser that is getting hot and work back from there.

 

[Zackman]

Re: How to find obstruction in cooling system

Why do you think you have an obstruction? 170F sounds normal to me for running at high rpms with a 160F thermostat. Also, the starboard riser will normally run hotter than the port side riser.

You may want to get an IR temperature gun and check the actual temperatures of the risers, manifolds, block, etc. to see what temperatures your actually running.​