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Poppet valve location XR6

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stearman

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"1994 150 XR6, SN OG104461. W

"1994 150 XR6, SN OG104461. Where is the poppet valve located on this motor? Can poppet valve problems cause the motor to run hot at low RPM (runs cool above 4000) Thanks for any help."
 
"Thanks, JB. I'll probabl

"Thanks, JB. I'll probably do T-stats and poppet valve first, see if that corrects the problem, then tackle the water pump. This is a DIY project, so I'm taking things slow at first. Thanks again."
 
"I think the poppet valve open

"I think the poppet valve opens at higher rpm's. After going thru my complete cooling system, my guess would be the water pump or thermostats"
 
"The poppet is opened by water

"The poppet is opened by water pressure from the water pump - below 4 psi the poppet remains fully "closed" and the thermostat(s) totally controll the cooling.

Between 4-9 psi (normally in the 1500-4500 rpms range roughly) the poppet opens/closes based on the pressure which pretty much (effectively) bypasses the thermostat(s) - the 'stats still work, it's just that the water channel that feeds the poppet is large enough that if it's open, the water takes the easy way out so the thermo's just sit there having little to no effect on the motor.

Above 9 psi (over 4500 rpms), the poppet is effectively "locked" full open and the water travels through the powerhead pretty much "unrestricted".

Knowing that's how the system works is valuable when troubleshooting the cooling system - and another solid reason why a water pressure gauge is a worthwhile retrofit on most motors - particularly the larger horsepowers that cost more than your tow vehichle should you need to replace them due to an overheat


Of course, the cooling system relies on the fact that the waterpump is serviced as it should be - none of that matters if the impeller hasn't been changed in years...."
 
"Thanks, Graham, for your disc

"Thanks, Graham, for your discussion about how the different parts of the cooling system work together. That stuff is like gold to a newbie like me! Based on your discussion, I'm going to go on and rebuild the water pump in my 150 XR6. I've already replaced both thermostats, but haven't run the boat to see if that helped. It has a water pressure gauge, and it never gets above about 10 PSI, all the way to WOT. And sometimes it oscillates very rapidly between about 3 and 10 PSI at around 4000 RPM. So I'm thinking I need to go on to the pump rebuild. Thanks again, Graham"
 
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