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Engine Temp Flucuations

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pro4mance

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"I searched the archives, but

"I searched the archives, but could not find any threads about this topic. My 1992 5.0 will only run near normal 160 degrees at WOT. At slower speeds it will the gauge will not move from the far left. Even after running WOT for 30+ minutes 1-2 minutes after entering a no wake zone the temp gauge drops all the way down again. Has this ever happened to you??? If so, what was the problem??? Thank you in advance for your advice."
 
"i had the opposite issue. 17

"i had the opposite issue. 170 at dock or no wake and dropped to 100 and back to 170 sparatically when moving along at different speeds. I checked everything i could. finally had tech look and he drilled a hole in the tstat lip. Now it only fluctuates down to about 130/140 and back to 170. I'm with hy on your issue. I'll bet your gas milage is terrible, right? Look for my link: merc 7.4 rebuilt "again". I got some great feedback from all these memebers."
 
"Hard to say! Only ran a shor

"Hard to say! Only ran a short test after drilled. Haven't been able to run it since. Yanked her in early September due to a hurricane scare and never made it back in. However, during the test run, The guage went from 170 down to maybe 150 and teetered back and forth very slowly. It never ran over 180 which was my initial concern. It used to hit 200 before and dropped down to 100 very quickly. i will replace the tstat with the hole in it next season. i think they used a Sierra tsat which concerns me a bit. Will replace with OEM."
 
"After reading all your advice

"After reading all your advice I checked intake hose for turbulance-I have it. Pulled alpha II off and changed impeller/checked for blockage. After back in water gauge seems to be running steady @ 160 with a 140 tstat. A buddy asked if I put any silicone on the inside of drive in between water intake and exhaust-I seen some on there but never put a fresh bead on. I had my hose off that went to my heat exchanger on my hot h2o heater and noticed that I have some exhaust in water jacket. I,m planning to pull drive again and silicone up. After engine has been rebuilt it seems not to b heatin my h2o heater up. Any advice?"
 
Plugged heater core; backflush

Plugged heater core; backflush it or replace it. Check hose nipples of hot water source and return for blockage.
 
Hope this is in the right thre

Hope this is in the right thread. I'm new to this forum. I have a 6 year old Glastron 175 with mercruiser 3.0 Alpha one. I just had a major service with new manifold/exhaust bellows/shift cable/ etc etc. The water temp before service was creeping up to 200 + then with corroded manifold I expected a big reduction. Now it runs at slow speed at around 185 but up to 200 if running at above 3500 rpm. What is the normal op temp for this engine/drive please?
Anything to check before I call the maintenance man who did what I thought was a good job?
Thanks Bob
 
Welcome Bob:

It is customar

Welcome Bob:

It is customary to start a new thread for your own boat problem; you'll get more responses since more people can see it. Did the tech. change the OD impeller while it was off?
 
"Bob...

Start a new thread

"Bob...

Start a new thread with the same question. Cut and paste it and you will get many more results than leaving it on the tail end of someone else's thread.

You need to know what t-stat is in your engine before you can tell what temp it should run at, but your's is getting pretty close to making steam. The easiest fix would be to put a new stat in it, and if that doesn't do it, then go for the new impeller next. After that things get a little more complicated.

Wrench"
 
"Thanks, I started a new threa

"Thanks, I started a new thread. To answer both responses, I had a new thermostat ( dont know what rating)and a new pump impeller"
 
Keith (original post).

Keith (original post). As stated... Sounds like you have a thermostat stuck in the open position or missing.
 
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