T-Stat for closed loop cooling system?

[RickyCru]

An aftermarket closed loop cooling system was installed on my 1998 Mercruiser 7.4l engine about 7 years ago. I recently replaced the water pump and thought I would replace the thermostat while I was at it. There was no thermostat installed. The boat has been running at about 153 degrees F and I know it should have a 165 degrees F thermostat (typically). I tried installing a thermostat and the engine heated to 200 degrees F + and I shut it down and removed the thermostat. So, it's now running at 153 degrees F again. I tested the t-stat in boiling water and it opened up, so it was good. Does a closed loop cooling system not require a t-stat? Am I losing power, efficiency and engine longevity running at 153 degrees F, in lieu of 165 - 170 degrees F?

 

[Scott Danforth]

It does require a thermostat

However the keed needs to be installed properly

What kit? What size HX (should be at least 5"in diameter and about 2 ft long)

 

[cyclops222]

D I Y fails again.

 

[RickyCru]

It does require a thermostat

However the keed needs to be installed properly

What kit? What size HX (should be at least 5"in diameter and about 2 ft long)

The brand appears to be “Monitor” and the HX is 5” in diameter and 21” long. What do you mean by keed?

 

[RickyCru]

D I Y fails again.

That was helpful (Not!). An experienced marine mechanic who was recommended to me installed a new engine in my boat 7 years ago and added the closed loop system, but did not install a t-stat. When I called him recently to find out why, he said it was too long ago and he couldn’t remember.

 

[Scott Danforth]

The brand appears to be “Monitor” and the HX is 5” in diameter and 21” long. What do you mean by keed?

typing on the phone with a cocktail in my hand would be the guess. I meant kit.

Monitor used to make HX's for Mercruiser before Champ (then Alpha Laval, and now whom ever is the parent company of Champ). Size should be ok for a half system.

how is it plumbed? until we have the pic uploads fixed on teh forum, you may have to used a 3rd party hosting and post the links.

a really slow video with a few panning shots posted to youtube helps. (no need to talk, just looking at the plumbing).

something is amiss with the plumbing if it overheats with a thermostat in it.

 

[tank1949]

You may have installed TS upside down.

 

[RickyCru]

typing on the phone with a cocktail in my hand would be the guess. I meant kit.

Monitor used to make HX's for Mercruiser before Champ (then Alpha Laval, and now whom ever is the parent company of Champ). Size should be ok for a half system.

how is it plumbed? until we have the pic uploads fixed on teh forum, you may have to used a 3rd party hosting and post the links.

a really slow video with a few panning shots posted to youtube helps. (no need to talk, just looking at the plumbing).

something is amiss with the plumbing if it overheats with a thermostat in it.

Thanks. The model number is MFH-5374. I checked the installation instructions on Monitor’s website and they state the t-stat is no longer installed in the intake manifold as the system comes with a new manifold cover elbow to replace the old t-stat housing and the t-stat is now included in the HX. Not sure where exactly in the HX components. I’ll call Monitor support and ask about the t-stat and temperature.

 

[Bt Doctur]

Meaning the housing has a restricted opening to regulate the engine temp, If you also install a stat it will overheat

 

[RickyCru]

Meaning the housing has a restricted opening to regulate the engine temp, If you also install a stat it will overheat

Is the 153 degree F running temperature in lieu of 165 -170 a big deal? Does it result in a loss of power?

 

[Scott Danforth]

Get an installation diagram. Without a thermostat, you need an orifice disc