Converting to closed cooling

[md240z]

I have a merc 5.7 EFI bravo 2 setup that I am converting to closed cooling. I have purchased a San Juan block only system. Before I installed the system, my engine was running 175 on the temp gauge. I have found that the gauge is not working correctly. So I purchased a point and shoot temp gun and found that the temp was around 155 at idle. The problem that I am having is that now when I run the boat at 3,000 rpms the temp climbs up to 176. When I slow down to an idle, the temp goes back to 155. The thermostat is a 160 and I have been told by several people the engine should run at 160. Has anyone seen this problem before or have any ideas as to what I can do to fix it?

 

[Lyle29464]

Re: Converting to closed cooling

sounds fine to me

 

[HT32BSX115]

Re: Converting to closed cooling

Howdy,

Welcome aboard!

I have a San Juan (full) system on my 454.

The temps you indicate are exactly what mine does.

I'd say you don't have a problem.

 

[Rocky_Road]

Re: Converting to closed cooling

I have a merc 5.7 EFI bravo 2 setup that I am converting to closed cooling. I have purchased a San Juan block only system. Before I installed the system, my engine was running 175 on the temp gauge. I have found that the gauge is not working correctly. So I purchased a point and shoot temp gun and found that the temp was around 155 at idle. The problem that I am having is that now when I run the boat at 3,000 rpms the temp climbs up to 176. When I slow down to an idle, the temp goes back to 155. The thermostat is a 160 and I have been told by several people the engine should run at 160. Has anyone seen this problem before or have any ideas as to what I can do to fix it?

It is not reasonable to expect the engine to run at 160 in your setup...that is the opening temperature for the thermostat only.

What you describe sounds to be just fine.

Happy boating!