Engine running cold with new thermostat.

[LS1_SE7EN]

I recently picked up a 1996 Ski Centurion. It has a 350 Magnum engine. It was running cooler than 120* before I put the thermostat in. My gauge starts at 120*. Now it will briefly warm up to ~135 and then immediately drop back down below 120*. It is a 180* thermostat. Is this normal? or should I be looking for something.

Thanks.

 

[maxxman04]

Re: Engine running cold with new thermostat.

if the t-stat is installed correctly, and it the right one, you may be looking at a faulty temp sending unit, or faulty guage. closed or raw water cooled?

 

[LS1_SE7EN]

Re: Engine running cold with new thermostat.

Raw water cooled. I sat with it idling and I could feel it warm up and then the thermostat opened and the area around it almost immediately dropped down to less than 120*. Possibly around 100* or so as it didn't feel hot to the touch. This happened repeatedly and corresponded with the gauge reading. The engine may be staying decently consistent in temperature. The sending unit for the gauge is right next to the thermostat. This seems like it would cause fluctuation in the gauge. I just thought it would be 160-180 degrees instead of less than 120 to 130 degrees.

 

[maxxman04]

Re: Engine running cold with new thermostat.

raw water cooled engines circulate 50 degree lake water constantly thru system, closed cool circulates the same 160 degree constantly.

 

[LS1_SE7EN]

Re: Engine running cold with new thermostat.

Ok. Didn't know if there was anything I was missing.

Thanks.

 

[bigskiohio]

Re: Engine running cold with new thermostat.

when i run on muffs my water is 60 deg or lower and my temp is barely 140 or lower. i not sure if my stat opens , how do you tell? raw water cooled?

 

[maxxman04]

Re: Engine running cold with new thermostat.

when i run on muffs my water is 60 deg or lower and my temp is barely 140 or lower. i not sure if my stat opens , how do you tell? raw water cooled?

generally, you can see a very slight temp difference on your gauge. temp will rise slightly, then decrease quickly. if temp gauge goes up and does not come back down, that is a good indication t-stat is not opening. although it could indicate other issues as well. and 60 degree water going in? did you actually measure the temp or just guess based on air temp? just curious

 

[bigskiohio]

Re: Engine running cold with new thermostat.

fill my pool with it so i have checked it before.

 

[maxxman04]

Re: Engine running cold with new thermostat.

fill my pool with it so i have checked it before.

nicely done. that is certainly one way to check.

 

[LS1_SE7EN]

Re: Engine running cold with new thermostat.

OK, I finally got around to getting an IR temperature gun. The boat has a new 160* thermostat in it. It works as it should (opens and closes correctly) The block only makes it to ~130* F. The manifolds/risers stay around 105*F. The water pump and thermostat housing jump between 85*F and 155*F. The heads stay around 170*F (measured close and right at the exhaust ports). The intake is around 150*F.

Again, my boat is raw water cooled and I understand that when the thermostat opens it gets a rush of ~79*F lake water. Do these temps sound OK? I am concerned that they may be on the cold side.

Do they make a thermostat that opens progressively versus one that is all or nothing? Something that would allow only a bit more cool water than is needed to cool the engine properly without adding a closed cooling loop? Or am I just over thinking this? I know it's not that big of a deal since it's not overheating or anything. But I don't want to waste a bunch of fuel and have accelerated engine wear because it was running too cold.

Thanks.

 

[Maclin]

Re: Engine running cold with new thermostat.

The way the cooling water bypass system works (or is designed anyway) with the thermostat the engine should be able to get to running temperature even in very cold water, just takes longer.

Seems that the thermostat may be allowing water past it, or there are some check balls or other items missing or hooked up wrong or backwards. These are just very general guesses.

LS1, is your boat an I/O or just Inboard?

 

[LS1_SE7EN]

Re: Engine running cold with new thermostat.

It is an inboard. I thought it was supposed to be able to get up there at least eventually. These temps were taken after a couple hours of boarding and surfing. The boat is currently in the water at a friends house while I get a little work done on the trailer. I could get pics this weekend.

The thermostat kit I got came with the gasket (of course) and a smaller felt o-ring. I also saw on the exploded diagram that there should be a sleeve of some sort that mine does not have. I thought that the 'kit" I bought would have that, but these things are sometimes misleading. It is the newest style housing.

Here: http://www.perfprotech.com/store/assembly/STANDARD-COOLING-SYSTEM,2334-100.aspx