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Just finished the following repairs to a Universal 5411 diesel on my 1980 Catalina 30. New oil sender, old one was leaking oil. New gaskets on manifold. installed a thermostat 140F because there was not one. Replaced temp sender. replaced old exhaust riser with new one. Tested the engine on the lake and now have steam coming from exhaust. Temp gauge shows temp at 140 to 150 F. Can anyone tell me why I have steam coming out the exhaust?
 

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Check the raw water intake. Take off the top on the inside strainer, then open the seacock for the raw water intake. Water should flow quite freely out of the open strainer. If not, then it's restricted. You can sometimes clear it by blasting hose water out through the raw water intake seacock. I just had this happen to me. With the seacock open, there was barely any water flow prior to blasting it out.

I would also check the impeller while you're at it. The thermostat could also be the culprit. Basically, it's running hot, so there is possibly a restriction to flow of the raw water, or the coolant is overheating. The heat exchange could also be blocked up. If the impeller is not intact, the pieces could be blocking that as well, or it could just be corroded.
 

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Possibly a leak anywhere in the exhaust or cooling system... Head gasket, exhaust manifold gasket, exhaust flange gasket... Are you sure that it is steam, and not smoke from a new part "settling in" to the engine?
 

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do you have water and steam or just steam coming out the exhaust. sounds like not enough raw cooling water to cool the exhaust so you get steam.
 

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The 5411 has a unique raw water system. With the thermostat installed, very little water will discharge until the engines warms up and the thermostat opens. Then it will spit water like any other engine. It's a little scary because almost nothing comes out at first and you think you're not getting water in. What little water is flowing into the exhaust can easily turn to steam from the exhaust gas heat. If its not getting above 150 deg it's probably alright. When it's up to operating temp you should see water coming out the exhaust.
 

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My Raw water cooled Yanmar almost always makes some steam. I assume because the moist, warm exhaust has higher humidity than the relatively dry, cool air of the SF Bay area. I guess if I was in Florida (for example), I probably wouldn't see steam. At least... I HOPE that's whats going on!
 

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My 3qm30 always through a little steam as well with temp gauge reading about 150. But I see plenty of water coming out as well. I am in humid conditions of Charleston so ahve wondered if that is a factor. I was thinking to borrow the wife's cooking thermometer to see what the water temp is as a way to check if this is a problem... I have checked inflow at strainer and it seems fine...
 

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The 5411 on my previous boat would show a little water vapor (steam) especially in the spring when the water was cold. I suspect it's common on raw water cooled engines because the water injected into the exhaust is much hotter than that of a fresh water cooled engine.
 

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Thanks everyone for your response.
I have owned this boat for 7 yrs. and had no steam problem till I installed new oil sender, new manifold gaskets, a thermostat, new temp sender and exhaust riser. The temp gauge reads 150 degrees and there is steam coming from the exhaust. Previously there was no thermostat. I am beginning to wonder if the thermostat is the problem. PO had a hose running from thermostat assembly back to the raw water intake seacock with a valve in the middle of the hose. I do not know why he had this done. You can open the valve and water will recirculate through the engine. If you close the valve water will run through engine and go out the exhaust. I am going to be on my boat on Tuesday and I will start the process of elimination. However I am not sure where to begin. Anyone have a suggestion?
 

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I have seen that valve setup discussed as a way to get the water heater to work better. Mine does not have the valve, and the engine makes hot water just fine, so I'm not sure why some boats have had a valve installed.
The standard setup is to have a tee on the water intake seacock, one leg going to the pump inlet. The hose from the bottom of the thermostat goes to the other leg of the tee. The hose from the top of the thermostat goes to the exhaust. If you have a water heater it's connected between the thermostat and the tee. Water will recirculate until the engine warms up and the thermostat opens. At that time water is discharged out the exhaust and is replaced with cold water from the intake. The only water discharged when cold is the little bit that goes through the bypass holes in the thermostat, and this may become steam in the exhaust. It's ok, that's how the system is supposed to work.
On most other engines, the recirculation takes place inside the engine and the raw water is discharged without going through the engine until the thermostat opens.
With the valve setup, the valve takes the place of the thermostat. You adjust the amount of recirculation manually to get the running temp you want, but this will vary with water temperature and load so it's not a reliable system.
 

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Thanks everyone for your response.
I have owned this boat for 7 yrs. and had no steam problem till I installed new oil sender, new manifold gaskets, a thermostat, new temp sender and exhaust riser. The temp gauge reads 150 degrees and there is steam coming from the exhaust. Previously there was no thermostat. I am beginning to wonder if the thermostat is the problem. PO had a hose running from thermostat assembly back to the raw water intake seacock with a valve in the middle of the hose. I do not know why he had this done. You can open the valve and water will recirculate through the engine. If you close the valve water will run through engine and go out the exhaust. I am going to be on my boat on Tuesday and I will start the process of elimination. However I am not sure where to begin. Anyone have a suggestion?
Ok, it sounds like the PO had ditched the t-stat in favor of manually regulating the engine temperature with that valve. Many Atomic-4 gas engine owners (also manufactured by Universal) do the same thing.

I'm not positive on this, but adding a thermostat and having this valve in the loop may create too much of a restriction. If you haven't done so already, make sure that valve is wide open. You might consider removing it altogether.

Second...I hate to ask this, but are you *sure* that you've installed the thermostat right side up and not backwards or anything?

Lastly, once the engine is at operating temp, hang a 5 gallon bucket over the stern and catch the exhaust water. If you're not getting at least 1.5 gpm at 700 RPM's idle and 2 gpm at 1000 RPM's, you may have crud in the exhaust manifold or an obstruction somewhere.
 

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The PO did indeed replace the thermostat with that manual valve setup. The thermostat on the 5411 put the system in recirculation mode and most water leaving the engine goes back to the water intake. Once the water comes up to temperature, the thermostat opens to let enough water out into the exhaust to maintain the set temperature.

What temperature were you running before? If it was lower than the current 150F, that could be the explain the "steam". And yes, with the thermostat, either remove that recirculation valve for leave it wide open.
 

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The stock setup is a little scary because almost no water comes out until the engine comes up to temp. You can't check for water flow. The only way you know it's to watch the temp gauge, and these engines don't come with alarms. As long as it doesn't go over 150 or so, all's well. Diesels really prefer to run at 180 or so, but in salt water that will scale up the engine, so raw water engines are always set for 140. 150 won't hurt it.
 

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Thanks for you input capt jgwinks. I know at one time in past years, before I took ownership, there was a water heater. That explains why the valve. Mystery solved !!! Now to solve the steam problem. Will begin tomorrow checking for water flow.
 

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BubbleheadMd and JimsCAL your input has also helped me understand what the PO did and why they did it. I think the problem may be the t-stat.
 

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The new thermostat does have bypass holes in it, right? Should be two oblong holes to let a little water through. If you want more bypass and more water coming out when cold, you can drill a couple more bypass holes.
You can check the thermostat by putting it in a pan of water with a thermometer, and heat the water on the stove. Should start to open at about 140 and close again when it cools.
 

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Thanks everyone for your response.
I have owned this boat for 7 yrs. and had no steam problem till I installed new oil sender, new manifold gaskets, a thermostat, new temp sender and exhaust riser. The temp gauge reads 150 degrees and there is steam coming from the exhaust. Previously there was no thermostat. I am beginning to wonder if the thermostat is the problem. PO had a hose running from thermostat assembly back to the raw water intake seacock with a valve in the middle of the hose. I do not know why he had this done. You can open the valve and water will recirculate through the engine. If you close the valve water will run through engine and go out the exhaust. I am going to be on my boat on Tuesday and I will start the process of elimination. However I am not sure where to begin. Anyone have a suggestion?
You keep saying "steam problem" as if steam is automatically a problem. That is not the case. You were asked a very important question : is it steam, or steam and water that is coming out. The latter might be normal.
 

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You keep saying "steam problem" as if steam is automatically a problem. That is not the case. You were asked a very important question : is it steam, or steam and water that is coming out. The latter might be normal.
That's the point I was trying to make. Sounds normal to me, it's just different than it was, and not normal for any other model engine.
 

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I dunno about the 5411, but the Atomic-4 has a "dual action" thermostat. The t-stat cap has a boss cut into it that allows the thermostat to physically move up and down, in addition to the spring plate opening and closing. This is the bypass that allows adequate cooling water to the exhaust. The thermostat doesn't have holes in the edges of the disc.

Edit: Nevermind. I see that the diesel thermostat is completely different.
 

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Capt JG, when the thermostat opens and lets the hot water out the exhaust does the thermostat close the bottom loop back to the T? Does your system have the $1850 Fresh water retrofit kit? When the water reaches 140 deg what prevents the water from continuing to recirculate back through the T, into the pump, and back into the engine resulting in overheating?
Mike Huss
 
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