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1994 Merc 74L 454 rebuilt recently again

"guy,

thank you. the one o


"guy,

thank you. the one on there now is definitely not molded. I'll see if i can search one out locally tomorrow. Is that a commonly stocked part, you think? Does that sound like it could be causing my problem to you?"
 
Tom:

You may have to order


Tom:

You may have to order it unless you go to a BIG marina repair shop. If the hose is flattened out some it would be fair to say it isn't helping it since it would become a "choke" point in the coolant flow!
 
"tom:

the lug (aka grom


"tom:

the lug (aka grommet) is embedded into the gaskets, at least on the ones I have. It works like a conductive button.

If the flush hose is on the pressure side of the pump, it should be ok. You have to be really careful with T's in the suction side"
 
If you are concerned with the

If you are concerned with the T remove it and put a straight piece of tubing int its place to do your testing.

If you have the thermostat housing that needs to be grounded by that embedded star washer in the gasket I would suggest for testing to get a heavy duty ring terminal that has a 3/8 diameter hole and will fit under the thermostat bolt hex head.

Make a ground wire attached to the ring terminal and go either to battery negative or a good engine ground. This will temporaraly prove/test the sender is grounded correctly.
 
Tom:

Kghost is right about


Tom:

Kghost is right about removing the Tee. I'd use the reinforced hose to keep the pump from sucking it flat.

The 2001 west catalog dicsusses flushing tees and seacocks. Sounds like your setup has caused more than one overheat. They suggest safety seacocks to eliminate the air leaks.
 
Thanks guys. This is getting

Thanks guys. This is getting rediculous now! I ran today after replacing the sending unit. Went to 180 - 190 deg and I turned back. Again ran out of time to do more testing. would the sending unit affect the temp gauge that prior to change said 170 at dock? I'm about ready to take up sailing!!!!!!!
 
"Okay, explain this to me! Go

"Okay, explain this to me! Got hold of the tech who had my engine rebuilt and put it in. Met him today. He used his ir gun and it seems the temps are all good. He hooked up a portable gauge panel and the guages worked like mine. After taking off the tstat housing and removing the tstat. it ran at a steady 120-130. there was a scaling of rust that had fallen from the housing or came from the manifold it sits on. it was removed. we ran again. Guage was at 170-180 until we got out of no wake zone. gauge was still dropping to 100 and back to 180. The gun read ok (150 ish)accept for a warmer port head 180ish. Tech (over 30 yrs exp.) drilled a small hole in flange of the 2nd new sierra tstat. enigine ran 170 with slight drop to 120-130 while running at different rpms.

Seems my gauge is about +10 deg higher than actual temp. I think that is normal!

What did the hole do and is it a bandaid?"
 
""Sierra""

""Sierra"" I would say something but I wont............

The additional hole either Bleeds steam or makes up for a questionable brand thermostat..........

The difference in the two head temps may be the issue. A 30 degree difference may be why you are seeing a 30 degree difference from normal. May be a restriction in the port water flow or possible a bad head gasket allowing some exhaust into the water at the head. This may also explain the need for a "bleed hole"

JMHO
 
"would the restrictione be fro

"would the restrictione be from the circ pump (supposedly new)? If i replace the tstat with a new one, what should i get (160 deg now)?

Also, should the gasket be replace everytime you access the housing? Is it just for a seal or does it serve another purpose. now water leaks. i ask because both timees it was access ed the same gasxket was on.
What are other signs of a head gasket other than smoke (which i do not have)?"
 
143 degree t'stat

Water


143 degree t'stat

Water like electricity will flow the path of least resistance. therefore my thoughts are that there is enough water comming in but one side is not allowing enough out...........that may explain the difference between left and right temp difference.

the only other thing I could think of is exhaust gas is getting into the incomming water stream causing air displacing some of the water.

oh your guage should read within 2-3 degrees of what it really is at the sender.
 
"If your engine is RAW water c

"If your engine is RAW water cooled, 143 degree t'stat. If it is a closed cooling system with a heat exchanger is should be 160 degree."
 
"K,

Thanks. it is raw cool


"K,

Thanks. it is raw cooled. you thinging head gasket regarding the exhaust? is lower tstat degree true that worse fuel economy.

Also, am i correct, based on your answer above that if I have a 143, the temp gauge should really never go over 145-150?"
 
Every boat I have ever driven

Every boat I have ever driven and the guage and sender works correctly they are allways 145-150. 160-170 when run hard for a long period of time.

FUEL ECONOMY with a 454??????????? Do not even go there!!!!

I will let others chime in on other possibilities. I am going to bed.
Did almost 300 miles on the bike today.......
 
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