4.3L brand new re-man engine running too cool??

[mtbdudex]

I just had a 4.3L vortec re-man engine installed in my 1996 Four Winns 170 Horizon. The guy who did the work suspected my temp gage as being bad, he said he put two theromstats in and a know working intake temp sensor.

I've put 2.5 hours on this engine, 1st hour at 2000 rpm or below, 2nd hour at 3000 rpm or below.
All on real lake in Brighton Michigan area.

Today, being the 4th, I decided to use my radio shack infra red temp sensor to see if the engine was getting up to "temp".

Set-up:
Driveway with hose for cooling thru I/O drive:

After I had the engine running 10 minutes took these readings:

83.5def f @ Intake manifold:

94.0 deg f @ rocker cover top:

89.5 deg f @ outside of exhaust manifold:

131deg f was hotest I could find, that was base of spark plug:

I'm inclined to think the theromstat is stuck open, and I should NOT run this anymore till fixed, cause there may be some engine damage going on, correct?

If the temp sensor was bad and thermostat working correctly, then the intake should be around 140deg f, correct?

Can I go to Murrays Auto tomorrow and buy a thermostat there?? Plus housing gasket.
(is there any diff between marine one and car one??)
thx for advice.

Here is cluster gage:

 

[gadget73]

Re: 4.3L brand new re-man engine running too cool??

I doubt you'll find a 140 at an auto parts store. West Marine does have them though. There are some oddball gaskets involved with marine thermostats, so you're best off getting the kit that includes all the stuff you need.

What sort of temperature do you find at the intake right near the thermostat neck? Thats usually the hot spot on the intake.

 

[mtbdudex]

Re: 4.3L brand new re-man engine running too cool??

I went to Wilson Marine right at 11am when they opened today, Grand River-Brighton, got a new thermostat/gasket, $20-ish total.

Installed, started in driveway again, temp came up slowly to 130deg f, more so when I measured the engine block by freeze pugs it was also same temp as temp gage. So, I trust the meter gage, and now cooling system working properly.

btw, the thermostat was definitely the old/original one from 1996, never replaced. Maybe I heard the mechanic wrong, Monday I'll inform him what happened. The engine/assy comes with 1 year warranty from him.

 

[mtbdudex]

Re: 4.3L brand new re-man engine running too cool??

Someone correct me if I am wrong but I believe that engine calls for a 160 degree thermostat.

My post may have mis-led you - sorry for that, when I saw the temp coming up to 130 deg f I knew:
a) the meter cluster temp gage was working One less thing to fix
b) the old thermostat was stuck open and that's why the temp never rose much at all, this one slowly was rising.

I shut it down at 130 deg f because being in my driveway did not make sense to run it for longer, I believe the problem is solved.

I did buy a 160 degree thermostat, the old and new one have that stamped into the face of the brass.

I'll be taking it onto the lake later today and see how long it takes for the temp to reach 160.

thx again.

 

[MikDee]

Re: 4.3L brand new re-man engine running too cool??

A 145*, thermostat is the proper one for a raw water cooled Mercruiser, a 160* thermo. is for a car, and a 180* thermo. is normally used for a Merc. closed cooling system.

You can let it sit in your drivreway all day long with the garden hose on it, usually and it won't even show up on the guage, if your system is working properly that's what I've found, but one trip on the water should bring the temp up, at least until it shows on the gauge.

 

[SPDFRK68]

Re: 4.3L brand new re-man engine running too cool??

I have an 89 dynasty with a 4.3 and it came stock with a 142 degree thermostat with i just replaced and the parts store were i got it from listed the same. And just for info Napa has a good selection for mercruiser parts.

 

[mtbdudex]

Re: 4.3L brand new re-man engine running too cool??

The online store showed a 143 deg thermostat, the parts guys at Wilson Marine said the 160 deg was the correct one. He double checked with my engine model#.

The old/orig one had 160 stamped on it, the replacement had 160 stamped on it.....

Therefore, I'm sticking with the 160, unless it's really a game breaker at ruining my new re-man engine.

Who's/What's "The authority" and "decision maker" here?

Engine spec's in repair manual?
(I don't have that yet)

edit:
I see "Bubba1235" posted the manual spec, it says 160 degrees.

 

[Don S]

Re: 4.3L brand new re-man engine running too cool??

Back in the 80's abd early 90's, they did use 142? Tstats. today with emissions and all, 160? is about minimum.
The other thing, on muffs, you may not get over 130?. No load there to help and the cold water from the hose keeps the temp down.
Once in the lake, and under a load, it will probably be running in the 160 to 175 range.

When reading with a temp gauge, read at the temp sender to check your helm gauge, not the valve cover, or intake.
A temp reading on the back of the heads and the fronts will give you a good idea where the temps really are.

And just for info Napa has a good selection for mercruiser parts.

If you happen to like Sierra parts, because NAPA does not carry OEM Mercruiser parts.

 

[Bifflefan]

Re: 4.3L brand new re-man engine running too cool??

A 145*, thermostat is the proper one for a raw water cooled Mercruiser, a 160* thermo. is for a car, and a 180* thermo. is normally used for a Merc. closed cooling system.

You can let it sit in your drivreway all day long with the garden hose on it, usually and it won't even show up on the guage, if your system is working properly that's what I've found, but one trip on the water should bring the temp up, at least until it shows on the gauge.

Just so you know since the late 80's early 90's, cars have gone to 195 deg therm's. I dont think you would want that high in a boat.

 

[MikDee]

Re: 4.3L brand new re-man engine running too cool??

I gotta disagree. I've never seen a GM boat engine that the thermostat was less than 160. 140 would be awful cold for the engine and would not yield very good fuel economy.

Straight from the manual:

Then you've made a blanket statement, without knowing the facts Bubba. Every Mercruiser I ever had, or been around in the past, called for a 142* thermostat as orig. equip., and that's what I used, apparently this has changed with some of the newer marine motors to 160* for emissions, or whatever, as Don stated.

Just so you know since the late 80's early 90's, cars have gone to 195 deg therm's. I dont think you would want that high in a boat.

Well Duh! No kiddin All land vehicles used a 180* thermostat as standard equipment, until the mid-70's when all the car companies switched to a 192* thermostat for better emissions, & better fuel milage, that is the standard nowadays, maybe you're too young to remember this By the way, anyone like myself who ever put a performance computer chip in their car, was told to get a 142* thermostat for best performance, and the only place available to get one of these was a marine supply. So, I was aware of this 20yrs ago.

 

[wca_tim]

Re: 4.3L brand new re-man engine running too cool??

a lot call for 140, but I've been running the hotter one to let oil temps get higher. with the cooler 140 degree thermostat oil temps weren't getting hot enough to boil off small amounts of condensation and it was building up in the valve covers. My current engine gets to 140 or 150 on the muffs with the 160 thermostat.

cars can run hotter thermostats because they have a closed, pressurized cooling system and so have a higer boiling point for the engine coolant.

too much cooling is not a good thing either....

 

[MikDee]

Re: 4.3L brand new re-man engine running too cool??

The trick is, in racing, with a lower temp thermo. it delivers a cooler denser fuel charge.

 

[mtbdudex]

Re: 4.3L brand new re-man engine running too cool??

Time "ran out" yesterday for the long weekend, so did not get the boat into the lake to see what temp the engine stabilized to after running for 15-20 minutes under load.

fwiw, my old thermostat outer housing and the new one's packaging.
You can see 160 stamped into the old one - original from 1996.

 

[mtbdudex]

Re: 4.3L brand new re-man engine running too cool??

When reading with a temp gauge, read at the temp sender to check your helm gauge, not the valve cover, or intake.
A temp reading on the back of the heads and the fronts will give you a good idea where the temps really are.

Good point, take my thermal reading where the intake temp sensor unit is, I'll make sure and do that next time.

fwiw, the 130deg f I took was on the engine lower block itself - right next to the core plugs (not freeze plugs). It seemed to be 130-ish +- all in that general area.

Thx guys, its good to be boating again and enjoying the outdoors!!