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Jerseydave
06-18-2012, 10:04 AM
On my '93 LT-1 it still runs at 120 degrees. (river temp is 68) Here's what I've done so far.

-Verified the guage works by touching the wire to ground.....guage pins to full temp.
-Replace sending unit for guage
-Replaced both t-stats....143 on bottom, drilled 160 on top
-Replaced steam tube at rear of engine with brass fittings and hoses. I cannot move the steam tube to the front of engine because of my high mounted alternator.

t-stat mixing housing at front of engine feels cold to the touch even after running 25 minutes.
Engine runs fine, no sign of overheating, no warning light or buzzer, no leaks.

I pulled the 160 t-stat to make sure its not stuck open and it's closed.
I have not checked the lower 143 t-stat to see if it's stuck open. Could that be it?

Table Rocker
06-18-2012, 06:18 PM
The only way I can think of that water could be circulating through the engine with the thermostat closed would be with the heater on (if you have a heater). The closed thermostat should keep cool water from entering the engine and it should warm up.

ahhudgins
06-18-2012, 06:38 PM
Just throwing this out there. Just because you ground the wire for the sending unit and the meter pegs, it doesn't mean that the gauge is accurate. If it were me, I would check the ACTUAL engine temp at the sending unit with an infrared gauge. If you find that the actual engine temp is 120 degrees, then you know itís a cooling issue. If you find that the actual engine temp is 143 (or 160, I donít know that engine) then you know you have a gauge or wiring issue. A dirty or corroded wire connection could throw the gauge off.

JimN
06-18-2012, 06:55 PM
On my '93 LT-1 it still runs at 120 degrees. (river temp is 68) Here's what I've done so far.

-Verified the guage works by touching the wire to ground.....guage pins to full temp.
-Replace sending unit for guage
-Replaced both t-stats....143 on bottom, drilled 160 on top
-Replaced steam tube at rear of engine with brass fittings and hoses. I cannot move the steam tube to the front of engine because of my high mounted alternator.

t-stat mixing housing at front of engine feels cold to the touch even after running 25 minutes.
Engine runs fine, no sign of overheating, no warning light or buzzer, no leaks.

I pulled the 160 t-stat to make sure its not stuck open and it's closed.
I have not checked the lower 143 t-stat to see if it's stuck open. Could that be it?

Any chance that one or both of the thermostats is in with the button on the wrong side?

Jerseydave
06-18-2012, 07:20 PM
Any chance that one or both of the thermostats is in with the button on the wrong side?

For sure the 160 is in correctly, I'm going to check the 143 to see if it's stuck open. I'm 99.9% sure I put it in right though.
Jim why would the temp sender be located so close to the water source? Seems to me that that area would always be cool since fresh lake water is constantly entering that housing.
I'm going to check it with a temp gun next time out on the water.

80371

Table Rocker
06-19-2012, 12:16 AM
I don't have a sensor on the mixer of my '96, only on the water pump. You are right, the water in the mixer would always be cooler.

Is that a temp sensor you can see just to the right of the mixer, inside of the elbow hose? That's where mine is.

Jerseydave
06-19-2012, 03:53 AM
I don't have a sensor on the mixer of my '96, only on the water pump. You are right, the water in the mixer would always be cooler.

Is that a temp sensor you can see just to the right of the mixer, inside of the elbow hose? That's where mine is.

The temp sensor is on the left side of the mixer, near the black hose in pic. (straight down from the words K&N on the spark arrestor)

Table Rocker
06-19-2012, 09:55 AM
What is that the arrow is pointing to? That is about where my temp sensor is, on the water pump. I wonder if you have two.

pram
06-19-2012, 12:58 PM
That is strange for sure to have a sensor on the mixer

my sensor is located where the arrow is pointed also

I do have to say though that mine seems to run colder also according to the temp gauge

took forever to warm up on sun when we went out

didn't want to kick out of high idle

Stx221
06-19-2012, 04:35 PM
The temp sensor that the arrow points to is for the ECM. There is another sensor somewhere for the gauge, but I don't know where it is located based on memory. As far as I know, the ECM and the gauge do NOT get a reading from the same sensor.

I can find the location of the other temp sensor for you this weekend when I have access to my repair manual. I wonder if the sensor for the gauge is off slightly, but the ECM is seeing the correct temps? Does the boat run well?

For what its worth, mine runs at approx 140 degrees all day every day...

1redTA
06-19-2012, 04:43 PM
gauge should be on the water pump the ECM should be in the head (car)

Jerseydave
06-19-2012, 05:17 PM
The temp sensor that the arrow points to is for the ECM. There is another sensor somewhere for the gauge, but I don't know where it is located based on memory. As far as I know, the ECM and the gauge do NOT get a reading from the same sensor.

I can find the location of the other temp sensor for you this weekend when I have access to my repair manual. I wonder if the sensor for the gauge is off slightly, but the ECM is seeing the correct temps? Does the boat run well?

For what its worth, mine runs at approx 140 degrees all day every day...

Correct, the sensor with the arrow in pic above is for the ECM. 2 wires, yellow and black.
The sensor I replaced is for the guage for sure. It does seem to me that sensor will always read a colder temp than the ECM sensor. Not sure why they chose to have those sensors where they are because they will never read the same water temp IMO.
The boat runs perfect. I will take a infrared temp gun out with me next time to check various engine temps in various locations on the engine.

Maybe some other LT-1 owners can see if their guage sensor is in the same spot, and post what your engine temp is when running the boat. Stx221, nice to know you're running 140 all the time....sounds about right for guage reading. I bet the actual engine temp is closer to 160 because of the top t-stat. Perfect temp.

langedp
06-20-2012, 08:13 PM
Posted a reply awhile back in your other thread in the electrical section. My '94 LT1 has the ECM sensor in the same place as yours but my temp gauge sensor is on port side engine head. My engine temp reads around 140 unless I run hard for awhile then it climbs up to 160 and levels off.

Jerseydave
06-20-2012, 08:35 PM
Posted a reply awhile back in your other thread in the electrical section. My '94 LT1 has the ECM sensor in the same place as yours but my temp gauge sensor is on port side engine head. My engine temp reads around 140 unless I run hard for awhile then it climbs up to 160 and levels off.

Thanks, I'll take a look tomorrow for it on the port side head.
If you have a pic of it that would be nice too. :D

So do you also have a temp sensor in the mixer like mine, or nothing there?

langedp
06-20-2012, 10:31 PM
There's nothing in the mixer. Here's a pic of the head with the sensor removed. I don't have one handy that shows it in place and the boat is up North. There's also a pic of the sensor itself. Not sure if this is a standard location either.

Dave

langedp
06-20-2012, 10:36 PM
Here's one of the engine. The sensor wire is laying on the carpet as I was trying to figure out my temp problems.

pram
07-06-2012, 04:26 PM
Maybe some other LT-1 owners can see if their guage sensor is in the same spot, and post what your engine temp is when running the boat. Stx221, nice to know you're running 140 all the time....sounds about right for guage reading. I bet the actual engine temp is closer to 160 because of the top t-stat. Perfect temp.

Posted a reply awhile back in your other thread in the electrical section. My '94 LT1 has the ECM sensor in the same place as yours but my temp gauge sensor is on port side engine head. My engine temp reads around 140 unless I run hard for awhile then it climbs up to 160 and levels off.

So I am not the only one who's gauge only reads 140 then. I would have thought that it would be at 160?

I have an infrared gun that I am going to try it tomorrow

formosa
07-06-2012, 04:50 PM
Mine is normally 140 ... 160 after running hard as well.

langedp
07-06-2012, 06:08 PM
So I am not the only one who's gauge only reads 140 then. I would have thought that it would be at 160?

I have an infrared gun that I am going to try it tomorrow

Now that the lake temp is warming up, the engine seems to get up to 160 faster. It holds there pretty well so things seem to have stabilized.

Jerseydave
07-06-2012, 10:15 PM
There's nothing in the mixer. Here's a pic of the head with the sensor removed. I don't have one handy that shows it in place and the boat is up North. There's also a pic of the sensor itself. Not sure if this is a standard location either.

Dave

I just have a pipe plug in my left-side cylinder head. It makes perfect sense to have the gauge temp sensor there and not in the mixer.

I have not had the boat out for a few weeks so I did not get a chance to test the actual engine temp with an infrared temp gun.

langedp
07-06-2012, 11:06 PM
I just have a pipe plug in my left-side cylinder head. It makes perfect sense to have the gauge temp sensor there and not in the mixer.

I have not had the boat out for a few weeks so I did not get a chance to test the actual engine temp with an infrared temp gun.

Is your sensor wire long enough to move it over? Just move the pipe plug over to the mixer.

Jerseydave
07-07-2012, 04:28 PM
Is your sensor wire long enough to move it over? Just move the pipe plug over to the mixer.

It should be long enough, I'll have to try that and see what my engine temp is then.

CC2MC
04-01-2013, 02:58 PM
Bump, What was the final solution for this engine problem, as mine barely gets to 120deg. I have not tried the Temp gun yet, but would like to know if something was figured out.

Jerseydave
04-01-2013, 08:33 PM
I never relocated my sensor to the cylinder head, but I did check it with the infrared gun. Cylinder head temp was close to 160 as I recall from last summer, but the area where the sensor is near the mixer was much colder. Boat always ran great, never ran hot. Sometimes at idle the guage would climb to 160 and then drop after accelerating. I assume everything is working as it should.

I may still relocate that sensor this spring and see where that takes me. I like to have accurate temp reading while using the boat. Don't want to overheat that LT-1!

JimN
04-01-2013, 08:49 PM
I never relocated my sensor to the cylinder head, but I did check it with the infrared gun. Cylinder head temp was close to 160 as I recall from last summer, but the area where the sensor is near the mixer was much colder. Boat always ran great, never ran hot. Sometimes at idle the guage would climb to 160 and then drop after accelerating. I assume everything is working as it should.

I may still relocate that sensor this spring and see where that takes me. I like to have accurate temp reading while using the boat. Don't want to overheat that LT-1!

You know your engine has two thermostats, right? If the second one is sticking open, it will never get warm.

Jerseydave
04-01-2013, 08:59 PM
You know your engine has two thermostats, right? If the second one is sticking open, it will never get warm.

I know, both are new and the engine does get warm at the pipe plug location in the left cylinder head (as checked by an infrared heat gun). I feel this is where my sensor should be, not at the mixer in front where constant cold water enters. Not sure why it's there, but I really should relocate it to the cylinder head to see if I get a more steady temp reading. Maybe the owner before me put it there, not sure.

JimN
04-01-2013, 09:00 PM
I know, both are new and the engine does get warm at the pipe plug location in the left cylinder head (as checked by an infrared heat gun). I feel this is where my sensor should be, not at the mixer in front where constant cold water enters. Not sure why it's there, but I really should relocate it to the cylinder head to see if I get a more steady temp reading. Maybe the owner before me put it there, not sure.

Is that the one wire sender or the two wire sensor? They go where the harness reaches and where it was located from the factory.

Snipe
04-02-2013, 09:22 AM
I pulled the 160 t-stat to make sure its not stuck open and it's closed.
I have not checked the lower 143 t-stat to see if it's stuck open. [/QUOTE]

I had to replace my impeller because the P.O. never checked it and it was pretty much torn up.
I want to check the hoses and the t-Stat, but after reading this, are there two T-Stats? I thought there is only one. this is a 5.7 Vortec Engine.

Table Rocker
04-02-2013, 09:36 AM
I want to check the hoses and the t-Stat, but after reading this, are there two T-Stats? I thought there is only one. this is a 5.7 Vortec Engine.There are two thermostats on the LT-1 engines. The LT-1 has two thermostats due to the unique reverse cooling where the water enters the heads first and flows out the bottom of the block.

Snipe
04-02-2013, 09:43 AM
Thanks. I guess that doesn't apply to me then. I need to find some impeller pieces because the P.O. never changed it. When I pulled it it had pieces missing. I'm a little concerned about engine temp now. What T-Stat should be in there and what should the gauge read? I just posted a new thread before I saw this one. Let's see who chimes in. Hope nothing is plugged up as the P.O. never mentioned a problem wit it running warm.

mikeg205
04-02-2013, 09:55 AM
Snipe here's the engine manaul link http://www.indmar.com/service-support/manuals/1994-2002.aspx

http://www.mastercraft.com/files/manuals/1998_OwnersManual-PS190-PS205-XStar-SammyDuvall.pdf

142-160 degrees... for t-stats

Snipe
04-02-2013, 10:05 AM
Thanks. I have the second one you mentioned, but don't really like that one. I have been looking for that first one ever since I got this boat. I'm new to Mastercraft (former Nautique owner) and they are a bit different. Can a guy buy one somewhere to keep in the boat? That's a lot to download.:toast::toast:

mikeg205
04-02-2013, 11:05 AM
You may want to call Indmar.. they may sell a printed one.. but I doubt it. I bought the clymers manual for $25

http://www.amazon.com/Clymer-Indmar-Inboard-Gm-Manual/dp/B000ENB3UO

Jerseydave
04-02-2013, 07:17 PM
Is that the one wire sender or the two wire sensor? They go where the harness reaches and where it was located from the factory.

Single wire Jim, and I don't think the wire will reach to the left side head. I would have to splice a longer piece to it. Is it worth it? I'm also afraid the the pipe plug may not come out of the head easily either. I live by if it's not broke, don't fix it (or break it worse)