Temperature-Cool

[victoryinerie]

1998 Merc 5.7
Bravo III

I have other posts on similar subject but I have more information since I took the boat out tonight to see what the acutal temperature is in the water vs. under the muffs. Again, sender is good, guage is good, thermostat is good.

With the thermostat in, boat temperature while running hit about 100, little less when I shut off the engine and turned the key to on the on position (engine not running) the guage would read 160 and cooled down slowly.

With the thermostat out, boat temperature while running hit about 100, little less when I shut off the engine and turned the key to on the on position (engine not running) the guage would read 110 and cooled down slowly.

The previous owner said he replaced the impeller and that he found pieces of it when he changed it out. Could there be other piece lodged somewhere that would cause what I am seeing?? I checked out the thermostat housing and did not see anything. Where should I be looking? Should I be looking around the recirclating pump??

I also checked the gaskets on the riser/manifold and verifed that there were only two openings vs. gaskets with 4 openings.

Any suggestion on where to start looking??

 

[Bondo]

Re: Temperature-Cool

Ayuh,... Does your t-stat housing use the spacer ring,..?? Is it installed properly,..??

 

[victoryinerie]

Re: Temperature-Cool

Yes, it uses sthe spacer ring (white sleeve with two holes in it) It was cracked I replaced it with a new one. The two holes are facing the front of the boat/theromstat. The grove was lined up so I am pretty sure it is on correctly.

 

[fsamie1]

Re: Temperature-Cool

Seems to me that your temp is right when engine is off. With thermostsat in, after you turn the engine off, how long does it take to get to 160? IF it reads 160 right away, your temp is right and something is interfering with your read out. I would yry to read temp directly out nof the sensor and bypass all wiring to the dash. If it takes a while for temp to reach 160, I think your thermostat is not sitting correctly or bad. See if it is closed when cold. Also, when starting engine cold with garden hose, feel the water coming out. It should be initially cold (thermostat is bypassed) and when engine warms up about 3-5 minutes, the discharged water wil get warmer if thermostat is working correctly. good luck.

 

[victoryinerie]

Re: Temperature-Cool

Already went down that path I also hooked up a seperate guage right at the back of the engine, only wiring was too the battery and sender and when I shut the engine off the reading went right to 160, no delay.

 

[victoryinerie]

Re: Temperature-Cool

Still trying to figure this issue out....
Talked to some local mechanics they think if the guage is reading less than 100 with the engine running and I shut the key off and click it righ back on and the guage goes to 160 the issue has to be with the sender? They thought maybe I have a wrong sender? Is there any way to check this? I do not have the receipt for the one I just purchased however it does act like the one I took out. They also suggested taking a wire and wrapping it around the sender and then to the battery ground to see if it works any different. I personally don't think it is a sender issue but for now I will try anything.

One question I have is, if the theromostat is open, is there any way that more cool water than hot water could be running through the thermostat housing causing it to read cold while the boat is running and than once I shut it off the hotter water gets into the thermostat vs. being pushed through? Could anything be plug on the cirulator pump in the front??

I am grasping here.....

 

[John_S]

Re: Temperature-Cool

You should be able to tell if the thermo housing is actually making a 60 degree swing just with your hand. I suspect it is not, and you are getting the correct reading with the engine off, and key on.

Did you use the special grounding thermostat gaskets? Did you try grounding the sender seperatly?

 

[victoryinerie]

Re: Temperature-Cool

I did use the special gasket, I am going to make sure everything is clean and good tomorrow. I am also going to ground the sender seperatly with a wire to see if it makes a difference.

I am going to use my hand or an IR gun to see if it acutally makes a 60 degree swing....

Will update more tomorrow hopefully with an answer.

 

[victoryinerie]

Re: Temperature-Cool

Took the thermostat housing off ensured the grounding gasket was getting contact by cleaning everything up, ran a ground wire from the sender to the ground on the battery. Ran the engine under muffs for a good 15-20 minutes taking IR readings all over the engine, the hottest spot I could get on the actual block itself was 135, the hottest the top of the thermostat housing ever got was 117, when I shut the engine off, however the temperature at the actual base of where the themostat actually sits was 147. The guage read around 100 +/- while running and when I shut off the engine it went to about 125. At this point I really don't think my theromstat is opening, at what temperature would it start opening? It has a 160 degree thermostat in there, is it the correct one? Again Bravo III with a 5.7 engine,1998, the previous owner changed impellers, is there just one standard impeller by chance could I be pushing too much cold water through?? Again I am just grasping here but nothing seems to make sense except everything seems to run normal, just too cold....

 

[victoryinerie]

Re: Temperature-Cool

The gasket that goes around the actual thermostat not the the thermostat grounding gasket, are they supposed to be the same thickness? The gasket I have at the actual thermostat is slighty thinner, could my theromstat be floating in there causing the temperature to be cool?

 

[fraannk]

Re: Temperature-Cool

Do you have a schematic of your thermostat housing? Is it one of the ones with the check balls?

It sounds to me that the thermostat is working correctly. My guess is that too much of the cool water is making its way over the temp sensor. Without knowing which thermostat housing you have it is hard to figure out where the water is bypassing and being allowed to flow past the temp sensor without going through the block.

In my case the cool water was bypassing through the check balls too much and not enough was making it into the block causing overheat. Yours is a better situation but you could run into trouble if your thermostat ever quit working because you would never get the high temp on the gauge because cool water is being allowed by the sensor.

I hope this gets resolved because I love learning more about all of this.

Frank

 

[victoryinerie]

Re: Temperature-Cool

I do not have a schematic of the actual housing itself, if it exists does anyone know where to find it. My cooling system does not have check balls in the hose.
Couple quick questions:
-If the thermostat does not open, meaning the water is not hitting 160 where does it go, if it is not going through the thermostat housing?
-If the senders does not get water on it, will it heat up at with the air temperature?
-If I run the engine, remove the sender should water start pumping out the sender hole?
-If I changed to a 140 or 180 thermostat would that tell me anthing at all...

I truely don't believe the water is getting hot enough to open the thermostat, is this possible?? Could it not be going through the ciruclation pump or something?

Just throughing some questions out trying to figure this out. I really don't want to take it to a boat mechanic, get it back and hear him say everything is normal...

 

[victoryinerie]

Re: Temperature-Cool

Can anyone tell me if my engines is supposed to have check balls?
1998
5.7
Bravo III

It does not, could this be the issue? If not is there any other type of restrictor that should be anywhere?

 

[victoryinerie]

Re: Temperature-Cool

Well after some frustration the issue is finally fixed....And of course it was something simple and stupid...I installed the thermostat the same way I took it off from the previous owner, the thermostat was installed right on the engine block well here it gets installed up in the T-stat housing, yes I am a dumb ### but at least everything is working well now....

Thanks for all the help.