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redlightning
06-25-2009, 04:52 PM
Ok....i replaced both of the t-stats in my boat. After doing this the motor ran at around 185 degrees. I noticed when i installed the new 160 degree t-stat that it was somewhat different than the one i removed. It was different in that the holes drilled in it were in the part that opens and closes and not in the side. I also noticed that the holes in the old thermostat were around 3/8 of an inch in diamater and the holes in the new thermostat were around 5/16. I removed the new tstat and reinstalled the old one. Boat ran cooler.
The temp would still jump up a bit occasionally when running across the lake for 20 min or so. Never got above 185 or 190.

I made the assumption that the dealer provided me with the wrong thermostat. So, i ordered another pair of t-stats for the boat and they just arrived. The 160 is exactly the same as the new one i purchased from the first dealer. I am not sure what to do about this.
Any suggestions would be appreciated.

captain planet
06-25-2009, 05:21 PM
Unless I am incorrect, the t-stat for an LT-1 is 143 degrees since it has aluminum heads. I wouldn't run that engine at that temp!

Craig
06-25-2009, 08:22 PM
The one that goes into the triangular housing directly above the raw water pump is 143 degrees.

The second one, mounted facing the bilge under the flame arrestor, is a special 160 degree t-stat. I just replaced the second one in my boat and ordered it from skidim.com, it had some holes drilled in it in the direction that water flows, I did not notice any holes in the side of it (didn't look for any either).

Did you put the right ones in the right places? Also, make sure your dealer gave you the right 160 degree t-stat.

scottkirbysavage
06-25-2009, 11:49 PM
Ordered both thermostats for my lt-1 from skidim this year and installed 4 months ago. Mine runs a constantly 160 degrees. Make sure your impeller is in good shape, transmission cooler intake screen is clear, and that your thermostats are installed facing the correct way. Goodluck!

PS.205
06-26-2009, 09:03 AM
I just changed both of mine and noticed the difference in the holes also. I haven't had one problem with the temps. It sits at a constant 160 degrees.

brat
06-30-2009, 10:21 PM
anybody got any pics of the thermostat location above the raw water pump ??

redlightning
07-02-2009, 12:26 PM
The thermostat housing is just below the flame arrestor. Large molded hose attaches to it and goes to, if i remember correctly the circulation pump.

Thanks for the input. I have checked and cleaned the transmission cooler. It did have some debris in it. I am glad someone else has seen the difference in the way these tstats are drilled. I am pretty sure that both dealers i bought tstats from got them directly from mastercraft. I am going to install a new one, maybe tonight and see what happens.

haayjay
07-03-2009, 01:26 PM
Also check the steam vent tube that runs from the thermostat housing to the back of the mortor were it is mounted to both cyclinder heads.This suplys cool water to the cyclinder head by a temp. synder. Make sure that the tube is clear and free flowing.

redlightning
07-12-2009, 11:29 PM
Thanks I will check that.

I am really frustrated with this LT1 motor. Too many odd ball parts. I cannot come up with an exact set of circumstances that causes the motor to run warm. Never seems to run over around 190.

Today i installed another new thermostat i ordered from a different MC dealer. Drilled like i mentioned before. Small holes. Motor heated up quicker than with the old t stat and went right up to around 185-195. Didnt go any higher. Idled out to in the marina and gassed up. Again i went back to the dock and reinstaled the old tstat. Back to around 160.

Strange thing though. Idled out of the marina and ran across the lake for 4-5 min at around 2800 rpm. temp is consistant at 160. Throttled back to idle for a brief minute then back up to around 2800 rpm. Temp slowly started raising. Kept this up for the next 6-8 min till it got up to around 190. Never went above 190.

Later, headed back to the dock. Again running at correct temp. Slowed down to idle in neutral for a couple of min, the temp started raising. Worked its way up to the 190 area again. Throttled up to get back to the marina and it stayed right at 180-185 for 8-10 min at 2800 - 3300 rpm
Throttled back to idle before going into the marina and to let the kids swim for a few before heading in. shut down the motor. Started it back up and it was up around 200. Let it idle for a min or so and it came down to around 185. Reved up the motor to around 3500 rpm and the temp came down quick. back to 160.

What seems to me to be some random symptoms is what i have been dealing with all summer.

I cant figure it out. I dont think i am getting the correct 160 tstat. at least i think. I am wondering, if the dealers are getting these tstats from MC, if thy could have gotten a mis marked batch or something. Old tstat could be bad and causing problem. New raw water impeller. I have looked pretty good for any obstructions in the system. I cannot say 100% sure. I have checked the transmission cooler a couple of times in the last month and there always seems to be something in it. Cleaned it today again before any of this. New 143 degree tstat. I did have the raw water pump and most of the cooling hoses off when doing maint. Could i have connected something incorrectly? I have gone over it and i cannot see anything that does not look right. Its all pretty logical.

I did order a new temp sending unit. I really dont think that this is bad, but i am going to replace it so i know what i have. Any ideas would be greatly appreciated before i set it on fire.

TMCNo1
07-13-2009, 12:11 AM
I may have missed it, but have you replaced the raw water pump impeller anytime lately?

redlightning
07-13-2009, 03:24 AM
Yes i did. In the spring i decided to do some preventative maint. and replaced the impeller.
Found out that whoever replaced it last (dealer) broke one of the screws that holds the cover on. I removed the raw water pump. Removed the broken screw and installed a new impeller. At the same time, i replaced both tstats. Maybe i should pull it out and check it.

Craig
07-13-2009, 08:51 AM
Have you seen any leaks anywhere? It almost sounds like you may be sucking some air in somewhere.

Have you had a dealer check your temperature sensing unit and compared it to what the ECM is getting? The temp sensing unit could just be giving your gage a slightly inflated value.

Also, mine heats up when I shut it down and sit for a while. It is called, heat soak, it happens because the engine is warm and when you shut it down there is no longer any cooling water circulating so it heats up a bit. It is totally normal and the temp should come back down after you idle your engine for a couple of minutes.

Mine runs around 160 most of the time. When it heat soaks it gets up to 180-185. Sometimes it will run around 140-150 at slalom speeds and then hit 160 when we slow down.

JimN
07-13-2009, 09:12 AM
Thanks I will check that.

I am really frustrated with this LT1 motor. Too many odd ball parts. I cannot come up with an exact set of circumstances that causes the motor to run warm. Never seems to run over around 190.

Today i installed another new thermostat i ordered from a different MC dealer. Drilled like i mentioned before. Small holes. Motor heated up quicker than with the old t stat and went right up to around 185-195. Didnt go any higher. Idled out to in the marina and gassed up. Again i went back to the dock and reinstaled the old tstat. Back to around 160.

Strange thing though. Idled out of the marina and ran across the lake for 4-5 min at around 2800 rpm. temp is consistant at 160. Throttled back to idle for a brief minute then back up to around 2800 rpm. Temp slowly started raising. Kept this up for the next 6-8 min till it got up to around 190. Never went above 190.

Later, headed back to the dock. Again running at correct temp. Slowed down to idle in neutral for a couple of min, the temp started raising. Worked its way up to the 190 area again. Throttled up to get back to the marina and it stayed right at 180-185 for 8-10 min at 2800 - 3300 rpm
Throttled back to idle before going into the marina and to let the kids swim for a few before heading in. shut down the motor. Started it back up and it was up around 200. Let it idle for a min or so and it came down to around 185. Reved up the motor to around 3500 rpm and the temp came down quick. back to 160.

What seems to me to be some random symptoms is what i have been dealing with all summer.

I cant figure it out. I dont think i am getting the correct 160 tstat. at least i think. I am wondering, if the dealers are getting these tstats from MC, if thy could have gotten a mis marked batch or something. Old tstat could be bad and causing problem. New raw water impeller. I have looked pretty good for any obstructions in the system. I cannot say 100% sure. I have checked the transmission cooler a couple of times in the last month and there always seems to be something in it. Cleaned it today again before any of this. New 143 degree tstat. I did have the raw water pump and most of the cooling hoses off when doing maint. Could i have connected something incorrectly? I have gone over it and i cannot see anything that does not look right. Its all pretty logical.

I did order a new temp sending unit. I really dont think that this is bad, but i am going to replace it so i know what i have. Any ideas would be greatly appreciated before i set it on fire.

If you have an owner's manual for that boat, read the section that shows what should be done before going out each time. One of the steps is check the oil cooler for obstructions. A couple of times in a month leaves an awfully high chance of having something in it, especially if you already posted that there's always something in it.

Make sure the raw water hoses are in good shape where they fit over the hull fitting, oil cooler, raw water pump and anything else. Also, make sure the hoses are able to tighten properly. If any have a spot where they stop tightening (from being cranked too tight), replace them.

You have no problem with the temperature sending unit and the one that feeds the gauge has nothing to do with what the ECM sees. Yours seems to be reading just fine but the 200+ temperature at startup is normal. That happens on cars and trucks, too and is called heat soak. The motor gets hotter than the coolant while it runs and when the raw water supply stops, the average temperature through the whole volume of the motor increases. It's not a problem and if you turn your car's key on without starting next time after it sits for a short time, you'll see that the temperature reads higher than normal.

If you idle for a long distance and the temperature climbs, just rev it a bit in neutral. Also, make sure the bleeder lines (the smaller diameter rubber hoses) are clear of any obstructions.

Craig
07-13-2009, 10:44 AM
You have no problem with the temperature sending unit and the one that feeds the gauge has nothing to do with what the ECM sees. Yours seems to be reading just fine but the 200+ temperature at startup is normal. That happens on cars and trucks, too and is called heat soak. The motor gets hotter than the coolant while it runs and when the raw water supply stops, the average temperature through the whole volume of the motor increases. It's not a problem and if you turn your car's key on without starting next time after it sits for a short time, you'll see that the temperature reads higher than normal.


This is what I was trying to get at and did not articulate well.

TMCNo1
07-13-2009, 10:44 AM
If you have an owner's manual for that boat, read the section that shows what should be done before going out each time. One of the steps is check the oil cooler for obstructions. A couple of times in a month leaves an awfully high chance of having something in it, especially if you already posted that there's always something in it.

Make sure the raw water hoses are in good shape where they fit over the hull fitting, oil cooler, raw water pump and anything else. Also, make sure the hoses are able to tighten properly. If any have a spot where they stop tightening (from being cranked too tight), replace them.

You have no problem with the temperature sending unit and the one that feeds the gauge has nothing to do with what the ECM sees. Yours seems to be reading just fine but the 200+ temperature at startup is normal. That happens on cars and trucks, too and is called heat soak. The motor gets hotter than the coolant while it runs and when the raw water supply stops, the average temperature through the whole volume of the motor increases. It's not a problem and if you turn your car's key on without starting next time after it sits for a short time, you'll see that the temperature reads higher than normal.

If you idle for a long distance and the temperature climbs, just rev it a bit in neutral. Also, make sure the bleeder lines (the smaller diameter rubber hoses) are clear of any obstructions.

In the same train of thought, most all front wheel drive cars with transverse engines, that don't/can't have crankshaft driven cooling fans, have electric cooling fans and come on at preset engine temp to cool the engine/radiator especially when the vehicle is not moving and air is not being forced thru the grill and into/thru the radiator. Most times when a vehicle sets for a few minutes after it has been shut off, especially during hot weather, no air is moving to cool anything, the engine will heat soak and the electric fans will come on at that preset temp to reduce the coolant temp in the radiator and the surrounding air/engine in the engine compartment. Boats don't have that feature and even if you leave the bilge blower running, it doesn't have the capacity to move that much air to cool the engine as a car fan would.