Suzuki thermostat keep or go?

jim dozier

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On a previous post discussed an overheating 87 Suzuki 85hp. Had to remove the cylinder head<br />because of blockages in the coolant passages of the head. Installed with a new head gasket and <br />tested this weekend. Had recently (Sept) installed a new water pump impeller and a new<br />thermostat. Got good pee stream, but during testing today engine alarm went off repeated at WOT <br />attempts again. Since I had my tools with me and I knew the bolts weren't frozen I removed the <br />thermostat on the water. The problem disappeared. Now my question. Do I replace the<br />thermostat or just leave it out. I live in St. Petersburg, Florida current ambient water temp in<br />January 57 degrees, air temp 40-50 degrees. Water temp in boating season May to Oct is about<br />80-88 degrees and air is 85-95 degree. The motor ran great today (the coldest day of the year) <br />without the thermostat, but as a rule I know they put them in there for a reason. But this is not<br />Sweden or Michingan, do I need to keep it?
 

gss036

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Re: Suzuki thermostat keep or go?

While you have it out, bring (boiling(?) water up to temp and see if the thermostat is opening, & at what temp. It could be sticking or was hung on something. I have had to replace the one on my Honda.
 

jim dozier

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Re: Suzuki thermostat keep or go?

Yeah, that was the first thing I did when I got home. It opened fully on the stove in a pot of hot water. However, I had poked it with a screwdriver on the boat so I don' t know if I loosened it up or not. My real question is, I know that the thermostat was part of the problem since its removal improved the situation. But if in this climate I can get away without one it would be one less problem to worry about. This thermostat was purchased in late Sept and has already seemed to cause a problem. <br />Go Bucs, we're in the Super Bowl!
 

Harry Blanchard

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Re: Suzuki thermostat keep or go?

They put the Thermostat in there to regulate the temp by controlling the water flowing through your engine. By removing it the water is probably passing through too quickly, resulting in a hot engine, but cool water temp. They are not very expensive, replace it and enjoy your engine for a lot longer.
 

NathanY

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Re: Suzuki thermostat keep or go?

When you overheated it did you check to make sure that you did not warp the head? These older Suzuki's do that sometimes when you blow a headgasket.
 

Walker

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Re: Suzuki thermostat keep or go?

If you had blocked water passages in a head then you have buildup in the rest of the water jackets. Run the motor in a barrel with water and a couple of quarts of CRL til the motor reaches operating temp. Cut it off and let sit til it cools down. Repeat this process 8 to 10 times and it will clean up the passages pretty good.
 

jim dozier

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Re: Suzuki thermostat keep or go?

Walker,<br />Although there were clogs in the coolant passages in the head which I removed (see discussion in previous post: Suzuki overheats at WOT only) I was able to visualze the passages in the block pretty good and they were remarkable free of deposits so I don't think that is the problem. I checked the head with a straight edge and it did not appear to be badly warped. I will check the compression and check the plugs and cylinder for evidence of water leaks, but the engine ran great. About the comment that removal of the thermostat may cause overheating of the engine but not the water because it moves too fast, the temp sensor is is contact with the metal in the head not the coolant so I wonder if thats true when the temp sensor didn' t go off after removal of the thermostat.
 

jim dozier

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Re: Suzuki thermostat keep or go?

Walker,<br />Although there were clogs in the coolant passages in the head which I removed (see discussion in previous post: Suzuki overheats at WOT only) I was able to visualze the passages in the block pretty good and they were remarkable free of deposits so I don't think that is the problem. I checked the head with a straight edge and it did not appear to be badly warped. I will check the compression and check the plugs and cylinder for evidence of water leaks, but the engine ran great. About the comment that removal of the thermostat may cause overheating of the engine but not the water because it moves too fast, the temp sensor is is contact with the metal in the head not the coolant so I wonder if thats true when the temp sensor didn' t go off after removal of the thermostat.
 

Walker

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Re: Suzuki thermostat keep or go?

Any buildup or scale in the water passages will cause the motor to overheat at WOT because it hinders the dissipation of heat from the metal to the water. Its like putting a layer of insulation along the passages. You have a lot more heat needing to be transfered at WOT than at slower speeds. This is mainly a saltwater motor problem but it can happen from freshwater, especially powerplant cooling lakes.
 
D

DJ

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Re: Suzuki thermostat keep or go?

jimd,<br /><br />The thermostat(s) are installed for a reason. <br /><br />Beleive me, if they could be taken out with no adverse results, it would have been done 40 years ago.
 

jim dozier

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Re: Suzuki thermostat keep or go?

All deposits have been removed. None in the block. What problems will occur if the thermostat is left out in a warm climate? If the motor ran great on the coldest day of the year down here, I don't expect to have a problem with it runnning cold in the summer. What can I expect if I leave it out, fouled plugs, enginge damage, or what? I'm looking for specifics here, not that someone read it in a book somewhere that it should be left in. I am aware that the thermostat is put there to keep the engine within a specific operating temperature and to speed warmup to the optimum temperature. But the engines are built for a variety of climates from the artic to the tropics. Anybody out there below the 30th parallel (warm climates) that has actual experience with the operation of outboards without the thermostat?
 

Walker

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Re: Suzuki thermostat keep or go?

Don't know about your particular engine, but on my 120 Johnson the rectifier is water cooled and witout thermostats the water doesn't get up to where the rectifier is.
 

roscoe

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Re: Suzuki thermostat keep or go?

jimd, in your original post of the 19th, you said that the alarm/warning buzzer went off. You did not say the engine was running badly or that the engine was overheating. <br /><br />It may be that you have a faulty temperature sensing unit or warning curcuit. <br /><br />Your manual tells you how to test to see if it is working, but there is probably no easy way to check if it is working properly and buzzing at the right temperature.<br /><br />If your engine was operating well with the thermostat in, then I would have the warning unit checked out or replaced.
 

jim dozier

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Re: Suzuki thermostat keep or go?

Roscoe,<br />The engine was running OK and the alarm would only go off when I went to more than 3/4 throttle. It would go off if I slowed down and would return if I sped up again. I felt the engine and the block wasn't too hot but the cylinder head seemed hot, but I didn't have a temp crayon. I didn't want to press it so I went back to the dock slowly and removed the thermostat to see what would happen. I was then able to speed around for 30-40 min at WOT with the motor running great until I got cold and came in. The sensor is working in that it isn't always on, but I don't know at what temp it was coming on. It alerted me to the original problem a couple of weeks ago which I believe I fixed (clogged head cooling passage due to deficient original head gasket design which has been upgraded with new Suzuki head gasket design with slotted pasage instead of single hole for exit water) and I don't know if the relatively new thermostat just got stuck, or if there are other gremlins at work here but the boat ran great for 30-40 min sans thermostat and it makes me wonder if I should bother to buy another.
 

jim dozier

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Re: Suzuki thermostat keep or go?

I did a search here on the forum for thermostats and read quite a few posts and learned a few things and still have a few questions. I am still in learning mode and know I don't have all the answers. These things I've found on the forum:<br />1. Thermostats apparently fail frequently, especially after sitting for more than 5 minutes of downtime in saltwater.<br />2. Some people insist they be replaced or bad things will happen like: <br /> Cold engine temps with/poor performance/uneven idling and running<br /> Hot engine temps because water moves too fast<br /> Uneven head cooling and subsequent warpage and bad stuff<br /> Fouled plugs and excess carbonization and bad stuff<br />3. Some people leave them out and don't report (on this forum anyway) problems anymore. <br />4. Some poor bast**ds have to remove the powerheads to get at them.<br /><br />I now believe my thermostat was sticking.<br /><br />These things I wonder about my engine.<br />1. The water has to come through my block, through my head, through my thermostat housing/(and thermostat if in) and out a single hole to exit down the side of my head to exit the engine. How then can removal of the thermostat cause uneven cooling if it is on the exit side of the system? <br />2. How does water moving too fast through the engine cause it to potentially run hotter as some have said. While the contact time might theoretically reduce the amount of heat absorbed, the increase in flow would more than make up for it in terms of calories removed. Recall we blow air at speed across radiator to increase the cooling capacity. Furthermore the exit flow of the thermostat housing seems to be controlled by the small (relatively) orifice on the exit side of the thermostat.<br />3. I would concede that in cold water the enginge might not get up to operating temperature and that would likely cause some grief but I don't think thats gonna happen in St. Petersburg, Fla. I don't do a lot of idling/trolling anyway, its usually 1/2 to WOT for my boating.<br /><br />So guys do I leave it in and replace it twice a year or do I leave it out and forget it?<br />Thanks to all who have replied.
 

Harry Blanchard

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Re: Suzuki thermostat keep or go?

As to how can water running through too fast cause it too run cold, try this test. Light a cigarette lighter and pass it under your palm rapidly. Next, keep it lit and pass it under your palm slowly. Did you notice any difference in the amount of heat your hand absorbed? Think about it.
 

jim dozier

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Re: Suzuki thermostat keep or go?

Harry,<br />Sorry, I don't buy your analogy (I also assume you meant too hot). The item (hand or cooling water) has to be in continuous contact to replicate or model the system. When you pass your hand through a flame more quickly the total contact time is less, and less heat is removed from the system. If you ran a piece of metal or say a stream of water continuously (I ain't gonna do this with my hand) over the flame at different speeds and then measured the total heat removed my guess is that more total heat is removed at the faster speeds even though the temp on/in the moving metal/coolant would be reduced due to shorter contact time.
 

roscoe

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Re: Suzuki thermostat keep or go?

Sorry Harry, that just doesn't hold water, or make any sense either.<br /><br />Seems like you've got a very good understanding of what is going on. The only question left is if the over temp sensor is working at the proper temp. I don't know what they cost, but you may want to replace it for peace of mind.<br /><br />I would check this out before I made a decision of going sans thermostat.<br /><br />If you can go without thermostat without further damage, go for it. But if the motor didn't do this before your overheating incident, I would think that something is wrong somewhere.<br /><br />A new engine will cost you $5-8000.
 
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