Choosing the right t-stat

[subcrx]

Just converted over to closed cooling system on an 87 omc cobra setup with a gm 5.7 350 engine. It can no longer use the style of thermostat that omc has set for it and omc never had a factory closed cooling system, so iboats doesn't list one for me to choose. Now It looks like it takes an automotive style thermostat. I went and got one for this setup and fired it up, Temp went way too high, Well over 3 quarters on the gauge, before it only went half way, and the half way mark was 150. Im guessing the heat rating on that one is way higher than that. Ive been looking on I boats and I dont know which one would be suitable for me. Or should it be running at a different temp now.

 

[Bondo]

Re: Choosing the right t-stat

Ayuh,.....

With a closed cooling,... I'd set it up to run 180?......

 

[subcrx]

Re: Choosing the right t-stat

wow, my gauge maxes out at 220

 

[Don S]

Re: Choosing the right t-stat

You want a 160? thermostat. That will allow the engine to run between 175 and 180? under load.
Changing to a closed cooling system on old engine has about a 50/50 chance of working and plugging up the heat exchanger (no, it won't flush out) so be carefull and watch your temp gauge a lot.

 

[subcrx]

Re: Choosing the right t-stat

its a brand new rebuilt engine I got out of a c1500 van. So it has never seen raw water before. Any advice of type of coolant to use?

 

[Don S]

Re: Choosing the right t-stat

Then it shouldn't be a problem. Regular ole Prestone works great, so does Dexcool. It's all up to you and what you want to run.

 

[subcrx]

Re: Choosing the right t-stat

so with the engine running 175 to 180 degrees under load im sure that will register that high on the gauge and will bug me when im out there. Are gauges available where those temps are the middle reading?

 

[WizeOne]

Re: Choosing the right t-stat

its a brand new rebuilt engine I got out of a c1500 van. So it has never seen raw water before. Any advice of type of coolant to use?

Use common 50/50 ethylene glycol. I would also add an overflow (coolant recovery) tank. Your cooling system will blow out some coolant. You can get them at your local auto parts store. You'll just have to find a place to hang it. It will also come with a radiator cap that is designed to work with the recovery system.

Hate to be argumentative on the thermostat, but I would go with the 180 Deg stat. I use one in my 5.0 liter Ford, with San Juan cooling system and the recovery tank and my motor runs smack on 180 deg. It does so, as per the stock guage and my infrared temp gun, whether I am idling, driving at WOT or pulling 4 skiers.

It also stays pegged at 180 whether the water is 40 deg or 85 degrees.

 

[Don S]

Re: Choosing the right t-stat

Both Merc and Volvo use 160? stats in their closed cooled systems. They also run in the 175 to 180 range. Why they don't use a 180? stat, I couldn't say. Probably because there is a little fudge factor that gives you some room for manifold corrosion or impeller wear, but still keeps the temp in the proper range.

 

[Bondo]

Re: Choosing the right t-stat

so does Dexcool.

Ayuh,......

I wouldn't pour that into an Enemy's radiator......
Even the people I know with late model Chevies have switched to the Green stuff.....

 

[subcrx]

Re: Choosing the right t-stat

Yeah Ive seen that dexcool doesn't last that long. Ive seen the green stuff hold together for years

 

[subcrx]

Re: Choosing the right t-stat

Running with the green now and with the 160 t-stat, Stays right where I like it. Thanks