engine not reaching operating temp

[menos22]

stbd engine will not get past 135-140 degrees. 1994 350 Sea Ray express bridge twin 7.4l 454 mercruiser bluewaters, hurth transmission with v-drives full fresh water cooling.
Here's the deal. Engine starts just fine, coolant is topped off, run at idel for 30 minutes or more and temperature will only get up to 130-140 degrees. Figure the thermostat is bad. temp. reading are the same at the gage and using a IR heat gun. Changed the thermostat, the original was 160 deg. replaced it with 160 deg. new gaskets and still not coming up to normal operating temp. Normally runs at 160-165. Port engine comes up to temp. with no problem. What am I missing here? I took the old thermostat to NAPA and they matched it up with the new one. Do you think its the thermostat, cant imagine why it will not reach 160 degrees. Any advise would be appreciated. Thanks in advance. Mike.

 

[electricaldoctor]

There is only 5* difference. Could it be that the engine loop going through your water heater is accounting for the temperature drop?

 

[menos22]

The Thermostat housing is only reaching 130-140 deg. using ir heat gun. That's a 30 deg. difference. My Stbd. engine does go through the water heater, what would be the issue there???

 

[sbw1]

The heat exchanger for the hot water heater causes the engine which makes your domestic hot water to run noticeably cooler. I've never measured the difference, but can see it on the dash board gauge.
Also, you can have the gasket installed on the wrong side of your t-stat and create a cold running condition. Check that it's properly installed.
And, debris can cause a t-stat to remain partially open creating unwanted cooling. This doesn't have to be much. On a raw water cooled engine, I stirred up some sand in shallow water and one engine ran cold. Replaced the t-stat and it was fixed. Later, I noticed some tiny grains of sand in the used part that held it open by a small amount.

 

[hottoddie]

Is this a recent new problem. 30 degrees is a lot of difference and I doubt the water heater can be the cause. I would try swapping the dash gauges to see if the reading moves to the other side. I know the infra red agrees but it's an easy swap.

 

[menos22]

Would it make a difference if the hot water tank was empty?? This problem started when I fired it up after de-winterization to get the bottom painted. Ran it about 1/2 mile to the haul out and it never got to temp, port engine came right up to 160 deg. After bottom pain took it back to my slip and temp never got above 135. Like I said new thermostat installed, new gaskets. Installed according to the book: Gasket with continuity rivets, housing, Thermostat, gasket, cover, and two bolts with washer. Again the new thermostat was purchased from Napa. It a 160 deg. stat.

 

[sbw1]

Would it make a difference if the hot water tank was empty?? This problem started when I fired it up after de-winterization to get the bottom painted. Ran it about 1/2 mile to the haul out and it never got to temp, port engine came right up to 160 deg. After bottom pain took it back to my slip and temp never got above 135. Like I said new thermostat installed, new gaskets. Installed according to the book: Gasket with continuity rivets, housing, Thermostat, gasket, cover, and two bolts with washer. Again the new thermostat was purchased from Napa. It a 160 deg. stat.

Debris causing a mildly open stat?

 

[menos22]

Thermostat is new and tested using pan of hot water.

 

[scoflaw]

Drive it like you stole it, the stat will open far enough to clear whatever may be stuck in there.

 

[Espos4]

Drive it like you stole it, the stat will open far enough to clear whatever may be stuck in there.

Although isn't this a "closed cooling" application?
There shouldn't be any debris in there.

 

[Handsome Transom]

Defective thermostat

 

[scoflaw]

Although isn't this a "closed cooling" application?
There shouldn't be any debris in there.

Probably the same crap that eventually plugs up heat exchangers. There really isn't anything else that would prevent the engine from heating up. Doesn't need to be held open by much.

 

[sdarc]

Swap thermostats from port to starboard. See if it follows. But I would do what hottoddie recommended first because easier.

 

[menos22]

I like the drive it like you stole it idea. Although will try swapping thermostats see what happens. Thanks for all the input. Will let you know how I make out with the tstat swap.

 

[Espos4]

The Thermostat housing is only reaching 130-140 deg. using ir heat gun. That's a 30 deg. difference. My Stbd. engine does go through the water heater, what would be the issue there???

How is the water heater plumbed in to the cooling system?

If it's on the "engine" side of the thermostat (like a car heater), then this could cause the issue that you are seeing.

If it's plumbed into the "heat exchanger" side of the cooling system, then I would think that the water heater could not be the cause of the issue.

 

[menos22]

The water heater is plumbed on the engine side. It has a hose from the engine to the water heater and a return hose back to the engine. Like I said before the water heater is empty and dock water has not been turned on yet. Just don't understand, all it is is a loop through a heat exchanger in the water heater.

 

[Handsome Transom]

So in addition to the crud blocking the thermostat theory. It would probably beva good idea to drain and flush the coldside.source of crud could be a number of things but first to come to mind is someone having used non distilled water to mix it to correct ratio from concentrate which would cause mineral buildups or topping up with af of differing composition

 

[menos22]

The new thermostat that was installed was tested in a pan of hot water it worked fine. When it was installed it was in the closed position, so it would be impossible for it to be stuck in the open position. The engine never got past 135 degrees, and the thermostat will not open until it reaches 160 degrees. Even if it were open you would think that after 30 minutes or so of running the engine would reach operating temp. Looks like Thursday will be a nice enough day to try the, "Run it like you stole it" theory. will let you know.

 

[menos22]

Probably the same crap that eventually plugs up heat exchangers. There really isn't anything else that would prevent the engine from heating up. Doesn't need to be held open by much.

 

[menos22]

Thanks for all the advice and tips on my cooling problem. Finally got a nice day and took Scoflaw's advice and "RAN IT LIKE I STOLE IT". Ideled out for about 15 mins, temp still around 135. Got up on plane and temps came up to 160 and stayed there. All is good. Thanks Again.