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1990 454 Overheating could it be the thermostat

contender31

Regular Contributor
I have a 1990 33 foot Tiara with twin 454 crusaders 33 hp. The port engine has no water coming out of the exhaust and yet the temp reading on the gauge shows 140. Could it be the thermostat not opening? I have changed the impellers, flushed the u coolers with vinegar, changed the thermostat and the raw water pump bearings seemed fine when I changed the impeller. Pretty frustrating after going through all this work in that tiny engine compartment. If the thermostat was a 180 thermostat could that be the problem?

Thanks and look forward to your help:confused:
 
Since you are in Fla. you are fresh water cooled I assume? I can't see how no water can be coming out but temp is that low. I suspect it would heat up further if you left it run. Once I had no water coming out of mine after winter and found that the sea water strainer lid did not seal and it was sucking air. I put a little blue gasket sealer around the lid and that solved the problem.
 
Since you are in Fla. you are fresh water cooled I assume? I can't see how no water can be coming out but temp is that low. I suspect it would heat up further if you left it run. Once I had no water coming out of mine after winter and found that the sea water strainer lid did not seal and it was sucking air. I put a little blue gasket sealer around the lid and that solved the problem.

I know it is puzzling, the temp does not rise above 150 on the gauge after running it for several minutes at various rpm. I am getting very little water flow throught the exhaust only a little steam and traditional type exhaust. After letting the vinegar solution sit overnight in the u coolers I ran a pressure garden hose through both ends of the coolers and both ran the same water flow rate with no sediment. That lead me to believe that the problem was not the u coolers. I am thinking about back flushing the entire sytem tomm just trying ti think of a way to do it effectively. Do you know a system that is effective to flush it? AS well if the thermostat installed was a higher temp thermostat would it limit the water flow assuming the thermostat wouldnt open until it reached the higher temperature? Confused at this point????:confused:
 
The engine thermostat has nothing to do with raw water flow. You need to solve the lack of seawater flow. Is the thruhull scoop clear of barnacles? HOw old are the risers?
 
The engine thermostat has nothing to do with raw water flow. You need to solve the lack of seawater flow. Is the thruhull scoop clear of barnacles? HOw old are the risers?

Yes the thru hull is clear and the risrs were just done. what is the best way to backflush the raw water sytem?

Thanks
 
Note : the sea strainer on this engine has a slight leak in it, one of the 4 rods that holds the basket in place had been sheared off and there is a slight leak in it. Would that create an air vacuum reducing the flow?
 
Note : the sea strainer on this engine has a slight leak in it, one of the 4 rods that holds the basket in place had been sheared off and there is a slight leak in it. Would that create an air vacuum reducing the flow?

That is your problem. 99% guaranteed. Bypass it completely to check it. Like I said my gasket was old and on correctly but it didn't seal properly. The tiniest bit of air will stop it, guaranteed. Mine is a 31 Tiara so it is very similar. The problem now is you have probably trashed your impeller running it dry.
 
vinegar to flush a raw water side? Never done that. Does it work? I always use acid.

I read it on a blog over the past 2 days - when I started the process i had limited water flowing and after doing the vinegar treatment the flow increased dramatically. I took my u coolers off to do the exercise.
 
The engine thermostat has nothing to do with raw water flow. You need to solve the lack of seawater flow. Is the thruhull scoop clear of barnacles? HOw old are the risers?

I have been reading about an acid process to flush out the coolers but everyone says you have to replace your zincs? are the zincs inside the coolers or what are they referring to?

Thanks
 
I have been reading about an acid process to flush out the coolers but everyone says you have to replace your zincs? are the zincs inside the coolers or what are they referring to?
 
It is simple to pull the zinc....9/16 wrench and it is out. If you can, you will unscrew the zinc pencil from the brass plug , do the wash and then re-use the zinc, assuming it was good to begin with.
 
The plain pencil is Camp's size E-0; usually much less than the pipe plug with the zinc. You should be checking them once a month. I usually just change them once a month - one overheat repair is usually more than 100X for a zinc pencil. real cheap insurance.
 
Happy to report the problem is solved, it was a leak in the raw water sea strainer. The pump was sucking air and a very small amount of water. I removed the sea strainers, acid washed, put new gaskets in and water is flowing like never before. Thanks for all your input.:)
 
That is your problem. 99% guaranteed. Bypass it completely to check it. Like I said my gasket was old and on correctly but it didn't seal properly. The tiniest bit of air will stop it, guaranteed. Mine is a 31 Tiara so it is very similar. The problem now is you have probably trashed your impeller running it dry.

Happy to report the problem is solved, it was a leak in the raw water sea strainer. The pump was sucking air and a very small amount of water. I removed the sea strainers, acid washed, put new gaskets in and water is flowing like never before. Thanks for all your input.:)
 
Awesome, mostly on this forum I'm asking the questions, not giving answers so it is nice to give back. When it happened to me I immediately went to the seawater impeller for the fix which is a PITA on the starboard engine and I was fuming when it didn't solve the problem, especially when I found a little gasket sealer was all that was needed. Careful of that impeller though, you may have shortened it's life running it dry. From what Ive read they are unforgiving with no water. There may have been enough in the housing to keep it from burning up.
 
The impeller is probably okay, for it was getting lots of water. The air that was mixing with the water causes poor cooling effect, which you've seen.

jeff
 
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