PDA

View Full Version : LT-1 Temp Saga Continues - Help???


redlightning
06-05-2010, 12:49 PM
I have been dealing with a temp stability issue with the LT-1 in my 94 225vrs probably since i have had it (3 years). The temp will gradually rise when the rpm of the motor increases above 2500 or so. I can take the boat out and wake board, ski and whatever we want to do. When you take out across the lake to get where you want to go or just for a ride, get the rpm's up the temp gauge starts to very gradually rise. I will usually get up to around 190 and stay there. When you back off the throttle and go back to idle the temp will then try to spike. Neutral and a few revs of the motor will start bringing it back down. I noticed this first time out this year that the starboard side exhaust manifold is hotter than the port side.

One more weird thing i delt with last year. I replaced both of the thermostats. I ordered thermostats from skidim and also bought some from my local dealer as well as another dealer out of state. Yes i bought 3 of each temp. Installed the first set. The motor idled up to temp quick and perfect. Take it out on the lake and it reacts completely different. It gets hot. Too hot. When trying to ski or at high rpm. Replaced the thermostat with the original one and it goes back to the previous pattern. I replaced the t-stats two more times thinking i may have gotten some mis marked or bad t-stats. Same problem.

Now here is what i have done. As i said replaced the t-stats multiple times. Yes, new impeller in the raw water pump. Not once but twice. I had to remove the raw water pump, because the mechanic who worked on it last broke one of the four bolts holding the cover on. Removed the broken bolt and installed a new one with the new impeller. Replaced all hoses that relate to cooling except the molded hoses from the combiner where the 142 t-stat is located. I cannot find them to purchase. Circulation pump is not leaking. Raw water pump is not leaking. Transmission cooler is clear. Water intake is clear. I have not been able to find any obstructions. If there are any they must ben inside the exhaust manifold and the motor i guess. I orderd a new crossover tube and moved it to the front of the motor to deal with the steam issue. New plugs. new wires. No water in the oil. New temp gauge sending unit. Tested the sending unit for the ecm and it seems within spec.

Help! Could the circulation pump or the raw water pump be creating this problem without any of the obvious indications? I am going to run some more tests today. I am going to do a compression check and check the fuel pressure. I think i have a miss at lower rpm. The motor seems to run rich and kind of acts like it has a lumpy cam. I also have a spark plug wire removal tool that i plan to use to check this problem. Not sure if these are related or seperate. How do you test the coil pack? Any tests with a meter?

I have scoured this forum for hours and found very good info, but still cannot get down to the bottom of this.........

83SuperSlot
06-05-2010, 01:15 PM
Mine does something similar normally. I have heard that it is normal so I just maintain it. I also have everything new on the motor. It does fine under throttle but when idling it gets hot. I have heard that it is typical for inboards - which is why trolling is not reccomended with an inboard. When you are idling for a while you should put it in neutral and increase the RPM so that it can pump enough water to cool the motor... Or, just turn off the boat instead of idling.. Hope this helps... Good Luck!

JLeuck64
06-05-2010, 01:43 PM
http://www.mastercraft.com/teamtalk/showthread.php?t=31626

(This thread gets interesting about page 3 or 4...)

redlightning
06-05-2010, 05:00 PM
83SuperSlot - I dont think this is normal. You might want to look at some past threads on heat issues. Maybe someone else can chime in on the subject.

JLeuck64 - Thanks for the suggestion. I did exactly what that post talks about with the riser tubes being moved to the front of the motor instead of the back. Most of the other discussion in that thread revolves around hot water shower and i removed mine to get it out of the mix while troubleshooting.

Today i ran a compression check and had around 130lbs on each cylinder. I dont think i have a problem there unless a leak down test would show something different. I also checked the fuel pressure. At idle i had around 42lbs. When running the gauge bounced around but stayed in that area and would jump up a bit at WOT. It would bounce between 40 and 50 psi.

redlightning
06-08-2010, 06:47 PM
I sure would appreciate some suggestions. I am at a loss as to the next logical step besides replacing the raw water pump.

Gofast
06-08-2010, 09:32 PM
Trying to think of what could lead to this.

I had an obstruction in the exhaust manifold that the dealer thought was a cause of my temp issue. My real issue turned out to be one of the thermostats sticking. They are cheap so I would replace both again just to be sure.

Also, how many hours on the boat? I know the circulation pump is not leaking, but could it be corrodied ( sp? ) Might be time to replace that too. I could be wrong, but the waterpump circulates the water through the block, the raw water pump just makes sure the water gets there. I know I had an issue when I left the drain plugs out of the block with the corrosion on the threads after 1 winter.

The temps rising when RPMs go up leads me to think thermostats and water pump...

Best of luck.

Rob

JLeuck64
06-09-2010, 10:11 AM
Have you pulled all of the smaller bleed hoses off the exhaust manifolds yet to check for restrictions? There are two smaller hoses on the fronts and the larger hoses on the rear are both connected together...

falconjeter
06-09-2010, 01:43 PM
I would suggest possibly replacing the water circulation pump but don't think that is likely the problem. Seems you have taken most of the water entry systems out of the equation, I see that you are left with only the water pump and the water exit system. Hook a hose up and run the boat out of water to make sure you are getting good flow out of the exhaust. also could check on the water if you can get the boat on a lift. Remember that the water input is only half the equation, if you have an exiting obstruction this will slow the amount of water throughput for cooling. Just some thoughts.... Also, I have the exact same boat and i think it tends to fluctuate temp between 150 and 180 on the gage during running and slow cruising. I know the raw water pump can move a lot of water, much more than the engine needs. You can try running with the T-stat out or look for some other obstructions in letting the water exit into the exhaust.

cdevro
06-09-2010, 02:06 PM
You all may want to check out my post (blown motor) under maintainance, engine drivetrain.
Check your strainer.

link. http://www.mastercraft.com/teamtalk/showthread.php?t=35978

burner
06-10-2010, 02:59 PM
yes, he is right.. check the strainer. Same thing happened to me, sucked up some weeds which caused a very similar overheating problem! you would be surprised just how little weeds can cause the engine temp to go dangerously high. Happened to me on a 94 prostar 190.. just take the hose that goes from the scoop on the hull to the engine off. There is a honeycomb looking strainer in there, any obstructions will be clogged up there.. All you need is a flat head screw driver to remove the hose clamp. Stick your finger or something in there to clean it out..Hope that helps..

Ski-me
06-10-2010, 03:19 PM
Does your top thermostat have a hole drilled into it? I think this is the 160 stat.....

Here is a thread on the same problem with my LT1

http://www.mastercraft.com/teamtalk/showthread.php?t=23352&highlight=temp

scottkirbysavage
06-10-2010, 11:23 PM
I have a 1998 190 with an LT-1. Runs 160 degress all the time. Replaced both thermostats last year with skidim replacements as precautions. I run at idle as well as idle cruising alot. Runs cool with out ideleng up. Hope this helps. If not message me.

Scott

Thrall
06-11-2010, 08:56 AM
Have you checked the basics yet to locate a partial blockage. Run it in the driveway. Water come out both exhausts at the same time? On the lake, one manifold get hotter than the other? Starboard hotter then look for an obstruction on that side. What's hotter mean, if you can still touch them then not too hot.
Is your temp guage correct? When running across the lake you maintain 190? Should be 160, maybe the sender's bad. Make sure of the hole in hte 160 tstat like Skime said.
Ever overheat or are you just watching the guage? You can tell the difference between a motor running 160 or 190-200 just by feel and the heat coming off.
The temp will rise when you come back to an idle after running hard, for a bit. My LT-1 did. Guage always read about 200 when re-starting a hot engine, then comes down (heat soak).

redlightning
06-14-2010, 09:51 PM
Gofast - I replaced the tstats three different times and purchased them from three different places.
Skidim, Local Mastercraft dealer and then another dealer in north carolina. The 160 is kind of different. The original one i am currently running has the hole drilled in the side of the body. The replacements all have the hole drilled in the piece that opens and closes. The size of the hole is different also. The hole in the old one is close to 3/8 the hole in the new ones are only maybe 1/4.
The boat is a 94 and it has around 300 hours on it. Happy to replace the circulation pump, just tired of throwing money and time at this problem. I have worked on cars as a hobby over the years and i have not ever seen a water pump go bad and not leak. I am certainly no expert though.

redlightning
06-14-2010, 09:56 PM
JLeuck64 - Yes i have pulled the hoses and checked for restrictions. I replaced these hoses when i moved the crossover tube to the front of the motor. Both are connected to the output of the blend manifold where the 142 tstat is located. So why would one side get warm and the other not.
Just talking it thru. Doesnt make sense to me unless there is a restriction in the exhaust manifold. If there is then there must be two issues. One dealing with the exhaust manifold flow and another the motor. Right????

redlightning
06-14-2010, 10:08 PM
falconjetter - Thanks for the suggestions. Yea, i am trying to make the call on the pump. I just am trying to justify it. The fact that both exhaust manifolds are different is a bit baffling to me when thinking about the circulation pump. I am a bit confused. I thought i have read posts from several people saying that the temp should be around 160 or 170 and stable except for heat soak.

cdevro - burner - thanks i have checked the intake several times looking for any obstruction. Never seem to find any. I have only found anything in the transmission cooler a couple of times.

redlightning
06-14-2010, 10:19 PM
Have you checked the basics yet to locate a partial blockage. Run it in the driveway. Water come out both exhausts at the same time? On the lake, one manifold get hotter than the other? Starboard hotter then look for an obstruction on that side. What's hotter mean, if you can still touch them then not too hot.
Is your temp guage correct? When running across the lake you maintain 190? Should be 160, maybe the sender's bad. Make sure of the hole in hte 160 tstat like Skime said.
Ever overheat or are you just watching the guage? You can tell the difference between a motor running 160 or 190-200 just by feel and the heat coming off.
The temp will rise when you come back to an idle after running hard, for a bit. My LT-1 did. Guage always read about 200 when re-starting a hot engine, then comes down (heat soak).

Thanks for the input Thrall - I think i have checked everything. I will pull it again this weekend and see what happens. It all looked good last season and i was having the same problem. Not sure i was looking real hard at the flow though.
The port side i can rest my hand on it and leave it there with no problem. The starboard i can rest my hand and it gets uncomfortable after 20 sec. I am going to pick up a laster thermometer this week and check the two sides with it. Temp sending unit replaced to the gauge. I have not replaced the one for the motor yet. I saw some specs here on the forum for checking it with a multimeter and i think it is good. Hole in tstat is good.
So your motor would heat up after going back to idle after running hard? How hot did it get? Would you just let it cool down on its own? I do expect it to get hot at restart (heat soak). Did your motor remain stable at 165 or 170 when running 3500 to 4500 rpm? Mine stays stable until i get over 3k.

redlightning
06-14-2010, 10:22 PM
Should i go to the dealer to get the engine coolant sensor that goes in the front of the motor or can i get this at an auto parts store?

JLeuck64
06-14-2010, 11:16 PM
Well then... if you want to take the time to pull the exhaust elbow off the top of the manifold you could look down into the manifold coolant jackets for just the cost of a couple of riser gaskets???

redlightning
06-15-2010, 08:56 PM
Well then... if you want to take the time to pull the exhaust elbow off the top of the manifold you could look down into the manifold coolant jackets for just the cost of a couple of riser gaskets???

Thanks for the suggestion. I will do it asap.

Thrall
06-16-2010, 09:07 AM
If the air/water was real warm, mine would go up to 170-180 if I chopped it down to an idle rightafter a hard pull, but not for long, then it would stabilize to 160.
Definately got something going on if youhave the same results with a new temp sender for the guage, although it's not getting hot enough to go into rpm reduction right?
In my experience, circulating pumps either work or they don't, same with rw pumps as long as the impeller is good.
Is it possible that the circulating pump was replaced in the past and is not a reverse flow like the LT-1 requires?
(Not sure if this is even possible, JimN would know) Just grabbing at straws here.
Partial blockage, evidenced by one side hotter is more likely though.

ahhudgins
06-16-2010, 05:57 PM
Thought I had posted this already but I donít know where it went??????
Sounds like you have two separate issues: A partial blockage in an exhaust manifold or hose, and a water supply problem. I would worry about the water supply problem first that is causing your temperature fluctuation. This is the time I would recommend the ďbucket testĒ and run your boat on the trailer. Fill a 5 gallon bucket with water and stick your hose from the impeller input (or transmission cooler) into the bucket and see how fast it will empty the bucket. I think about 10 seconds is average at idle. My boat is at the lake so I canít verify that time. If you check it with a garden hose, the water pressure will be forcing the water into the system so itís not a good test of your impeller system. My boat sucks a garden hose flat even at idle. When I was putting the boat on the trailer this weekend, I checked the tops of my risers with an infrared temperature gauge and they were 130 and 140F. They get warmer as they get closer to the exhaust hoses. Temperature at the sending unit was 140F also. Readings at idle.

My transmission cooler is mounted horizontally and Iíve had a few weeds get into the cooler and they clung to the outside edge and at the bottom. The strainer looked clear until I removed the cooler and stuck a pair of bent nose needle nose pliers into the cooler and pulled several chunks of weeds from around the edge of the strainer.

Iíve seen a lot of exhaust problems caused by an old piece of impeller vane getting stuck in the ports on the thermostat housings. Itís also a good chance that youíve just got some rust and gunk in one of your manifolds.

TX.X-30 fan
06-16-2010, 08:41 PM
Be better if you had a raw water intake chewing up your trailer bunks!!

redlightning
06-16-2010, 10:43 PM
Thought I had posted this already but I donít know where it went??????
Sounds like you have two separate issues: A partial blockage in an exhaust manifold or hose, and a water supply problem. I would worry about the water supply problem first that is causing your temperature fluctuation. This is the time I would recommend the ďbucket testĒ and run your boat on the trailer. Fill a 5 gallon bucket with water and stick your hose from the impeller input (or transmission cooler) into the bucket and see how fast it will empty the bucket. I think about 10 seconds is average at idle. My boat is at the lake so I canít verify that time. If you check it with a garden hose, the water pressure will be forcing the water into the system so itís not a good test of your impeller system. My boat sucks a garden hose flat even at idle. When I was putting the boat on the trailer this weekend, I checked the tops of my risers with an infrared temperature gauge and they were 130 and 140F. They get warmer as they get closer to the exhaust hoses. Temperature at the sending unit was 140F also. Readings at idle.

My transmission cooler is mounted horizontally and Iíve had a few weeds get into the cooler and they clung to the outside edge and at the bottom. The strainer looked clear until I removed the cooler and stuck a pair of bent nose needle nose pliers into the cooler and pulled several chunks of weeds from around the edge of the strainer.

Iíve seen a lot of exhaust problems caused by an old piece of impeller vane getting stuck in the ports on the thermostat housings. Itís also a good chance that youíve just got some rust and gunk in one of your manifolds.

Thanks! I am going to pull the boat this weekend and look at the water flow out of the exhaust and try your suggestion of the bucket test. I agree it does seem to be two problems. I have been looking at the flow of the water thru the system. the water flows from the raw water pump to the mix manifold where the 142 tstat is located. From there both exhaust manifolds are fed. Since only one is getting warm i think there may be an obstruction in the manifold. I think i will pull the riser this weekend also and check it.

I have not been able to find any reason the motor would not be staying stable besides some type of flow issue. I checked the compression and didnt find any evidence of head gasket issues. No water in the oil.

I did find out from the dealer that the motor did overheat when the previous owner had the boat. That is what made me check the compression. The circulation pump looks like the original. All painted gloss black and no evidence of ever being removed or replaced. i wonder if the impeller cratered and peices went into the system. Could this damage the circulation pump?????

I will also double check the transmission cooler as you mentioned. I was pretty thourough, checked it several times but maybe....... thanks for all the temp data and suggestions.

ProTour X9
06-16-2010, 10:55 PM
I didn't read much of this thread but my old LT1 heated up when the impeller went bad.

JLeuck64
06-17-2010, 02:21 AM
I did find out from the dealer that the motor did overheat when the previous owner had the boat. That is what made me check the compression.

Now THIS is interesting...
Funny thing about sealing the combustion chamber is it is really hard to tell when the head gasket is no longer doing its job with just a compression gauge. Unless of course the head gasket has completely failed. With my experience, being mostly automotive, I have seen some head gaskets that are starting to fail, as well as some cracked cylinder heads, allow combustion gases into the cooling system. It's easier to tell because you can see the foam being pushed out the radiator filler neck. Looks just like the head on a cold glass full of beer! This would be much harder to diagnose on a boat of course because of the cooling system design differences...

I would think you might get a little indication from a spark plug if it was a sealing issue. Warped cylinder head or block surface allowing some water to enter that cylinder would tend to make that spark plug look cleaner than the rest.

Tougher to diagnose without some disassembly would be a cracked cylinder head... I suppose a guy could pull the exhaust manifolds off and take a look inside the exhaust ports before going to all the trouble of pulling the heads off the block for a thorough inspection. i would expect to see the same indication of the port with a problem looking cleaner than those that are ok.

But that statement from the dealer is coming a little late in the game as far as I am concerned... I mean gee whiz, does he know how long you been chasing this! For crying out loud!!!:mad:

ahhudgins
06-17-2010, 09:24 AM
I will also double check the transmission cooler as you mentioned. I was pretty thourough, checked it several times but maybe....... thanks for all the temp data and suggestions.
I know you've checked the cooler already, but I've seen this problem too many times to count. Just a few blades of grass or weeds around the lip of the strainer can cut down the water flow about 10%. I wouldn't panic just yet about a head gasket or a major engine problem until you test the boat on the trailer. If no one else rings in, I will do the bucket test this weekend and see how fast it pulls the water out. If you are worried about one manifold being hotter than the other, I'm sure you can pull the riser off and clean out what is blocking it.......look for that old piece of impeller in the thermosat housing port first!:D
Keep us posted.

blackcreek
06-17-2010, 05:45 PM
Thanks! I am going to pull the boat this weekend and look at the water flow out of the exhaust and try your suggestion of the bucket test. I agree it does seem to be two problems. I have been looking at the flow of the water thru the system. the water flows from the raw water pump to the mix manifold where the 142 tstat is located. From there both exhaust manifolds are fed. Since only one is getting warm i think there may be an obstruction in the manifold. I think i will pull the riser this weekend also and check it.

I have not been able to find any reason the motor would not be staying stable besides some type of flow issue. I checked the compression and didnt find any evidence of head gasket issues. No water in the oil.

I did find out from the dealer that the motor did overheat when the previous owner had the boat. That is what made me check the compression. The circulation pump looks like the original. All painted gloss black and no evidence of ever being removed or replaced. i wonder if the impeller cratered and peices went into the system. Could this damage the circulation pump?????

I will also double check the transmission cooler as you mentioned. I was pretty thourough, checked it several times but maybe....... thanks for all the temp data and suggestions.

The drivers side upper manifold will get warmer at idle on the lt-1. The bypass hose from each head dumps into the drivers side upper manifold. The bypass is not regulated by the thermostat, it pumps out the air bubbles and warm water all the time. At idle and low water flow the hot bypass water will heat up the drivers side manifold more than the passenger side. The hose that goes to the passenger side also rids the system of air but that water is cold water before going into the engine. You can put your hand on the small bypass hoses and feel the temp difference. Once you rev the motor up to cruising speed the water flow increases and the small amount of bypass does not affect temp difference. At cruising speed the manifold temps will be the same due to the large amount of water cooling the manifolds. If you pull off of cruising speed and immediately check the manifold temps they will be the same. Once you idle for any length of time the drivers side exhaust manifold will heat up to around the cylinder head temp. I made direct readings at idle on my lt-1 (see thread) 115 pax side at idle and 165 for drivers side. They even up after a high speed run.
http://mastercraft.com/teamtalk/showthread.php?t=33959&highlight=lt-1
It sounds like you have checked everything except the engine water pump. I would pull it and check for obstructions or foreign objects. I replaced my pump this year because the impeller inside the pump looked really rusty.

redlightning
06-17-2010, 07:30 PM
The drivers side upper manifold will get warmer at idle on the lt-1. The bypass hose from each head dumps into the drivers side upper manifold. The bypass is not regulated by the thermostat, it pumps out the air bubbles and warm water all the time. At idle and low water flow the hot bypass water will heat up the drivers side manifold more than the passenger side. The hose that goes to the passenger side also rids the system of air but that water is cold water before going into the engine. You can put your hand on the small bypass hoses and feel the temp difference. Once you rev the motor up to cruising speed the water flow increases and the small amount of bypass does not affect temp difference. At cruising speed the manifold temps will be the same due to the large amount of water cooling the manifolds. If you pull off of cruising speed and immediately check the manifold temps they will be the same. Once you idle for any length of time the drivers side exhaust manifold will heat up to around the cylinder head temp. I made direct readings at idle on my lt-1 (see thread) 115 pax side at idle and 165 for drivers side. They even up after a high speed run.
http://mastercraft.com/teamtalk/showthread.php?t=33959&highlight=lt-1
It sounds like you have checked everything except the engine water pump. I would pull it and check for obstructions or foreign objects. I replaced my pump this year because the impeller inside the pump looked really rusty.

I see where you are going with this, however my boat is the 225VRS. This motor is inverted and has a v-drive. The pass side is where the crossover tube dumps and it is the cooler of the two. I am going to pull the riser and see what i see over the weekend. I have checked the thermostat housing good as well as the blend manifold where the 142 goes. I have had every hose off as well as the raw water pump and replaced all the hoses except for the molded hoses.

blackcreek
06-17-2010, 09:17 PM
If your motor faces the other way around it would be the other side. Just letting you know that the cylinder head bypass side will normally run hotter at idle on the LT1. I did have some rust inside my mixing manifold. One side opening was quite a bit smaller until I cleaned out the rust. If you need to, getting the water pump off the motor is actually quite easy as there are no belts to mess with, don't know how much room you have on your boat but the 205 was not bad at all.

redlightning
06-17-2010, 09:35 PM
If your motor faces the other way around it would be the other side. Just letting you know that the cylinder head bypass side will normally run hotter at idle on the LT1. I did have some rust inside my mixing manifold. One side opening was quite a bit smaller until I cleaned out the rust. If you need to, getting the water pump off the motor is actually quite easy as there are no belts to mess with, don't know how much room you have on your boat but the 205 was not bad at all.

Thanks! I appreciate the input.

redlightning
06-26-2010, 05:51 PM
I ran the boat today and watched the temp closely. Never ran over 180 maybe 182. It would stay solid at 160 until a long run across the lake at 4k rpm. Then would slowly creap up to 180. It would spike a bit after a run at higher rpm then dropping to idle.


I pulled the riser from the exhaust manifold that is running hotter. I can find no obstructions. I did find a bit of crud just inside the brass connection to the riser. I went ahead and installed one of my 3 new 160 tstats while doing this.

Started the motor and checked for good flow from the crossover tube into the riser and it seemed good. When I pulled that small hose from the rises water came from the hose and also came from the riser brass fitting.

Let the motor idle and sure enough the temp slowly went up to 185. I have done this before and I know if I reinstall the old tstat it will go back to working as before.

So stil same problem. If running at 180 to 185 at 4k rpm is correct then no problem other than the one exhaust bank running hotter and installing a new tstat causes the motor to run hot. Btw just a reminder I have 3 new 160 tstats all purchased frm different places. Skidim, local mc dealer and another mc dealer.

I bought a new water circulation pump but have not installed it yet. I have no idea how old the tstat is and with what I see as some irratic temps I wanted to replace it thnkng t could have been the problem.

Wha do you guys think?? Pull the plug in the middle of the lake and swim for it.

redlightning
06-26-2010, 06:14 PM
Just for grins I just installed another of my new 160 tstats with the same conclusion.

redlightning
06-26-2010, 06:24 PM
Reinstalled the old tstat and it's idleing at around 150

redlightning
06-26-2010, 06:40 PM
The hose from the motor and from the crossover tube are pretty hot the others are relitivly cool.

redlightning
06-26-2010, 06:56 PM
The water does flow thru the v drive gear box.
Is there a way to check this for obstructions.
I don't see any way to check it.

1redTA
06-26-2010, 09:48 PM
The crossover tube is important to the lt1, it helps keep hot spots out of the heads and to bleed air out


I know you have replaced the t stats and temp senders how about a diff temp gauge to make sure the gauge is reading right?

redlightning
06-26-2010, 10:13 PM
I didn't read much of this thread but my old LT1 heated up when the impeller went bad.

Impeller is basicly new. I replaced it twice last season working on this problem. Thanks

redlightning
06-26-2010, 10:17 PM
The crossover tube is important to the lt1, it helps keep hot spots out of the heads and to bleed air out


I know you have replaced the t stats and temp senders how about a diff temp gauge to make sure the gauge is reading right?

I installed a new crossover tube when i moved it from the back of the motor to the front. I routed the output of the crossover tube into the drives side riser. The same one that is getting hotter. I guess i could try a different gauge. The weird thing is the difference in the temp's with the new tstats. It is consistant. Old one works pretty well, some fluctuations in temp. Up to 180 - 185. New one idles at 180+. I didnt even take it out and run it with the temp going that high at idle. I did rev the motor trying to see if it would come down.

redlightning
06-26-2010, 10:29 PM
The drivers side upper manifold will get warmer at idle on the lt-1. The bypass hose from each head dumps into the drivers side upper manifold. The bypass is not regulated by the thermostat, it pumps out the air bubbles and warm water all the time. At idle and low water flow the hot bypass water will heat up the drivers side manifold more than the passenger side. The hose that goes to the passenger side also rids the system of air but that water is cold water before going into the engine. You can put your hand on the small bypass hoses and feel the temp difference. Once you rev the motor up to cruising speed the water flow increases and the small amount of bypass does not affect temp difference. At cruising speed the manifold temps will be the same due to the large amount of water cooling the manifolds. If you pull off of cruising speed and immediately check the manifold temps they will be the same. Once you idle for any length of time the drivers side exhaust manifold will heat up to around the cylinder head temp. I made direct readings at idle on my lt-1 (see thread) 115 pax side at idle and 165 for drivers side. They even up after a high speed run.
http://mastercraft.com/teamtalk/showthread.php?t=33959&highlight=lt-1
It sounds like you have checked everything except the engine water pump. I would pull it and check for obstructions or foreign objects. I replaced my pump this year because the impeller inside the pump looked really rusty.

Blackcreek - I was mistaken. I changed the riser i dumped the crossover tube into when i moved it to the front of the motor. I found the same crud you discussed in your thread. I orderd a new one and routed the water into the drivers side riser. My motor is inverted in the rear with a v drive. I pulled the riser off the exhaust manifold today and didnt find any obstructions.

I am going to check my manifolds as you did and see if mine are similar to yours. Maybe i dont have a problem. I need to check it running and see if the temp stabilizes as you mentioned.

Thanks

redlightning
06-26-2010, 10:32 PM
I did the bucket test and the 5 gallon bucket drained in 44 seconds at idle. I started the clock when the motor kicked over and stopped it when the bucket was empty.

I also checked the water flow out of the exhaust. Both sides seemed pretty consistant. Water coming out all the time then bursts of water about every 5 seconds.

I bought a new circulation pump. I think i am going to install it tomorrow morning. anyone thinks this is a bad idea?

I think i will pull the blend manifold and look it over again while doing this job. Man i look forward to working between the back of the boat and the motor. Very tight. Mastercraft really should have come up with some other way to handle the raw water pump in the v-drive boats. It is a real ***** to work on.

1redTA
06-27-2010, 07:31 AM
Take one of your old thermostats and drill the air holes in it a little bigger. We used to do this on LT1 cars to make a cheap lower temp thermostat. It takes some trial and error so start with a slightly bigger drill bit

redlightning
06-27-2010, 12:17 PM
Take one of your old thermostats and drill the air holes in it a little bigger. We used to do this on LT1 cars to make a cheap lower temp thermostat. It takes some trial and error so start with a slightly bigger drill bit

Its interesting you suggest this. The old tstat has a hole probably 5/16 in size. The new tstats have a hole maybe 1/4. Still hard for me to believe that would have this big of an impact. Once the tstat opens it should provide adequate flow. My thought at this point is that possibly the circulation pump is not pumping as well as it should and not creating the flow needed. I am down to the raw water pump and the circluation pump. I am not really sure a raw water pump can go bad. Maybe the impeller can be bad or the bearings.

redlightning
06-27-2010, 01:48 PM
Just pulled the water pump and the mix manifold. No obstructions to be found anywhere. Opened up the water pump and everything looks good. Probably waisting my time replacing it but i already have it all apart.

redlightning
06-27-2010, 05:46 PM
I really really hate this LT-1. So installed the new water pump. Skidim didnt have it and suggested i buy it at auto parts store. Bought it at Napa. Everything is going smoothly until i go to reinstall the mix manifold. Apparently the casting is somewhat different and it is wider than the stand off position for the mix manifold bracket. Screwed!

redlightning
06-27-2010, 07:32 PM
Fired it up and ran it outside my shop with a bucket. Pulled the hose from the vdrive so the transmission cooler is still in the mix. Same problem. Old tstat idles at correct temp. new tstats were headed about 185. Didnt let it go any further. Could i possibly have three tstats from three different sources that are marked wrong? I think i pan tested them last season while i was working on this problem. Still thinking about pulling the plug and swimming for it. Ha ha.

redlightning
06-27-2010, 10:42 PM
I decided to run tests on my tstats again. I have two 142 tstats. Neither of these fully opened until the temp in the water was around 175. One never opened as much as the other. Seems that +/- 1/4 inch is fully opened. These barely opened even at 150.

The 160 tstats seemed pretty consistant. I have 4. The original one, and three i have purchased from three different sources. At 170 these barely opened up 1/16 of an inch.
At 180 - 185 they fully open.

The original tstat is the only one that keeps the motor the most stable. It will run 160 - 170 most of the time. bumps up to 180 when running at higher rpm for long distances. then some spiking when coming off plane from that type of run.

I see two differnences when comparing them. the orignal tstat and one of the 4 open the most. 1/4" +. The original tstat has the hole drilled in the side instead of the top and it is probably just shy of 1/4". The new tstats have the holes in the top and are at least 1/2 that size.

Thrall
06-28-2010, 09:33 AM
That svcks man. Sounds like you've covered every base multiple times. FWIW I don't think the size or location of the hole in the 160 stat is that critical. I put an automotive 160 stat in my LT-1, don't remember the size of the hole, but don't think it was 1/4" even that I drilled and she ran like a champ for years with that tstat in it.

redlightning
07-05-2010, 11:31 PM
Well.... Ran the boat a bit with the new water pump and it seems maybe could have been the problem.

Not sure what happened today though. Pulled the boat up to table rock lake for a couple of days. Boat was running great. Started pulling my kids on a new tube. Some aggressive turns and such. Next thing I know the boat shut it's self off. Looked at the temp gauge and it was at 240. I religiously watch the temp gauge with all the issues I have had with cooling. I bet I didn't go 1 to 2 min without glancing at it. Had to get towed in. Also now my stereo does not work. I had to reset the breaker next to the ignition switch. When I select the accessory position my gauges go all the way to the right. Something isn't right.

Tore into the cooing system and I don't see any problems. I was thinking thru what happened just before this mess. I made a long hard right turn. Is there any possibility that the water pick up could get out of the water when doing this? I hope the motor isn't baked.

Redstorm
06-11-2012, 09:37 PM
Well.... 2 years later, what happened? Did you sink the boat? LoL

Prostar 205
06-16-2012, 01:20 PM
Been following this thread, I have a very similar problem with my 99 LT1. Today I pulled the t stat housing apart and there was only 1 t stat the top one 160d. So there should be 2 t stats in this housing a top 160d and bottom 142d? Which way does the bottom t stat face? Could this lack of a t stat cause my erratic temp problem?