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Thread: 2.5 150 too cold at idle?
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09-26-2019, 09:07 PM #15000 RPM
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2.5 150 too cold at idle?
I’m in the process of rigging a 2.5 150 and putting it on my varmint project. When running the engine, I’ve noticed that it never really gets to operating temp, 95°F - 100°F according to my infrared temp gauge, after a 15-20 minute run time. Tell tale stream is pretty much instant on start up, and does get lukewarm to the touch. Water pressure gauge is about 8 PSI and steady. Brand new impeller, and thermostats. The thermostats are aftermarket ones with the tiny bypass holes in them. Is it possible that the poppet is stuck open? I’d like to see a little more heat in this motor, not really in the mood to cold seize it. Any ideas?
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09-26-2019, 10:53 PM #26000 RPM
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8 sounds high for idle, open popets should have it very low under 3.
But 8-9 is normally open pressure......
i would look for whats shooting pressure so high.
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09-26-2019, 10:58 PM #35000 RPM
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09-27-2019, 03:15 AM #4Member
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Just went through a similar situation with a 92 150XR6.
Water pressure 6psi at idle and would not increase with engine rpm. Replaced T stats with Merc brand t stats. Replaced poppet valve diaphragm and spring. Now have 2psi at idle and water pressure increases with engine rpm. At idle you should have about 2 to 3 psi, somewhere north of 1500 rpm is when the poppet valve begin to come into play and you should see somwhere around 9psi. At WOT water pressure should be a min of 12. Sorry I cant be more specific but I dont have my manual handy. Hope this helps
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09-27-2019, 07:02 AM #55000 RPM
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09-27-2019, 04:07 PM #6Member
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Here is an additional tip about your condition. Higher than nromal water pressure at idle can cause a rough idle condition also. If your engine is carbed it most likely will have a Thermal Air Valve on the odd cylinder bank. If CHT. doesn’t reach 100 deg. The valve wont open and port air to the carbs to lean the mixture out. Just an fyi for you.
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09-27-2019, 04:10 PM #75000 RPM
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88/12 reaction 19 (sold)
77 hydrostream varmint 2.5
02 Caravelle interceptor 212 5.7 GI-B
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09-27-2019, 04:32 PM #8Screaming And Flying!
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I would verify t-stats opening correctly in a pan of hot water. 143 deg is correct for most v-6 mercs.
83 V-King, 96 Mariner, 200 hp ff block 2.5 w/a 28p choppa
We gotta clean this liberal mess up, VOTE TRUMP TO MAGA!
Rebuild thread:
http://www.screamandfly.com/showthre...-it&highlight=
http://www.screamandfly.com/showthre...cs.&highlight=
Videos
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09-27-2019, 04:38 PM #95000 RPM
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XstreamVking liked this post
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09-27-2019, 04:42 PM #10Member
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Only one of those ports on the TAV has a hose connected to it. The other port is open to the atmosphere. If that valve is not connected to your carbs you probably need to re-Set the idle mixture screws after replumbimg the valve to the carbs. Do you have a maintenance manual for that engine? I would highly recommend getting one if you do not.
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09-27-2019, 04:43 PM #11Member
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Good point!! On the after market T stats.
Last edited by Iron Horse; 09-27-2019 at 04:45 PM. Reason: Additional info
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09-27-2019, 04:44 PM #125000 RPM
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09-27-2019, 04:52 PM #135000 RPM
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09-27-2019, 10:49 PM #14
I agree with poppet and double check stats. If either dont fix. its in adapter
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09-27-2019, 10:50 PM #155000 RPM
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