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Old 10-21-2010, 03:02 PM
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Default Poppet Valve

I have been having issues with my 225 efi Mercury overheating at high RPMs. I have changed the poppet valve twice. The first time I forgot to get the diaphragm (which had a small hole in it) needles to say it still over heated. So I changed it again (this time I remembered to get the diaphragm) as well as all the parts again. I haven't had a chance to try it out and see if it fixed it, but I do have a question to ask on here. Both times I took the poppet valve out I noticed that the grommet was not seated in the carrier. I have a new carrier but did not install it yet (mostly because I don't know how to get it out of the motor). Does anyone have any ideas why the grommet would be coming off the carrier? It is a new grommet. Thanks!

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Old 10-22-2010, 04:41 AM
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anything?
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Old 10-24-2010, 05:56 AM
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no ideas?
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Old 10-24-2010, 06:36 AM
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Originally Posted by brilloduck11 View Post
anything?
Bad poppets usually result in overheating at low speed not high. You may have something else going on.
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Old 10-24-2010, 11:19 AM
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Originally Posted by lostsinker View Post
Bad poppets usually result in overheating at low speed not high. You may have something else going on.
Lostsinker- Are you sure?
I thought the thermostat controls most of the low speed engine temp control with poppets closed, and at higher speed the poppet valves come into play by being pushed open by higher pump pressure so as to bypass the restricted thermostat passages to substantially increase cooling water flow .

So I'd think a bad poppet would either be stuck open and create excess low rpm cooling or be stuck closed and have no effect at low rpm but contribute to higher rpm overheat, no? No expert here, just asking.

Sorry , I can't help with the grommet and carrier issue, but the water passages may be too clogged for the poppets to be effective , or possibly there is a pump issue that is not delivering enough high rpm pressure?
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Old 10-24-2010, 12:30 PM
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TTaxi, you are correct. The poppet opens at high rpms due to higher pressure to allow more water to flow. Water pump has been replaced and pumps plenty of water through the tell tale hole. I'm just trying to figure out why the grommet it becoming dislodged from the carrier. I'm going to try to get the carrier out and replace it.
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Old 10-24-2010, 12:40 PM
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TTaxi, you are correct. The poppet opens at high rpms due to higher pressure to allow more water to flow. Water pump has been replaced and pumps plenty of water through the tell tale hole. I'm just trying to figure out why the grommet it becoming dislodged from the carrier. I'm going to try to get the carrier out and replace it.
That's not my understanding.
The poppet valve is normally closed allowing water to circulate through the heads. As the engine revs increase, the water pressure also increases. The flow is too much for the motor to pass so the popet opens and redirects some water to bypass the cooling channels.
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Old 10-24-2010, 01:33 PM
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There are different style poppit valves in Merc 225s, make sure you either have the right parts for your housing or purchase a complete kit that includes the housing. I replaced mine last summer and didn't get the right diaghram style the first time.
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