Poppet valve operation

[dazy_cutter_45]

The poppet valve actually opens and freeflows water thru the engine in a sense bypassing the thermostats, correct? At what pressure should it open and how much should the pressure drop? My overheat buzzer has gone off at cruising speed, around 4K rpms, twice. Hasn't at idle or at WOT and when it does I'm showing around 8psi water pressure. Gonna have a look at the waterpump tomorrow , maybe 10 hours on it, and do some backflushing of the block while I have the lower unit off. Not sure whats going on

[EuropeanAM]

In order to answer engine specific questions, it's necessary to know what engine you have (preferably including the serial number).

[dazy_cutter_45]

XR6 0T529180

[dazy_cutter_45]

I got it straight I , think. Seems I got jacked by Mercury and was to stupid to see it. My new water pump kit #96148A8 came missing a gasket. I got 2 top gaskets for the bottom plate and no lower gasket and didn't pay enough attention to catch it. I kept all the parts old and new and once I got it down and really started looking it was pretty obvious. I put it back together with the old gasket and now about 7+ psi at idle versus barely moving the needle. I suspect at mid range it wasn't building quite enough pressure to open the poppet and the thermostats couldn't keep up with the heat load,,,,,,,,,,FYI, shit happens, don't assume anything and look at least twice

[dazy_cutter_45]

I would still like to know how the poppet system should work not knowing for sure will bother me forever now ignorance is not always bliss

[RiverRatMD]

7+ at idle!?

[dazy_cutter_45]

7+ at idle!?

That's on muffs, not in gear so I expect it'll be less normal operation, and splitting lines on the gauge also so maybe closer to 6#s. Next live run Monday or Tuesday, we'll see

[RiverRatMD]

Ahhhhh..Muffs!!!! Got'cha! I would expect 2-3 psi myself, but I'll wait and see what you end up with....I usually test run a motor in tub myself, I don't use muffs. Good luck & be safe!

[Nova Kaw 650]

I would like to know a little more about poppet valve operation as well. What actually causes it to open?

[EuropeanAM]

I got it straight I , think. Seems I got jacked by Mercury and was to stupid to see it. My new water pump kit #96148A8 came missing a gasket. I got 2 top gaskets for the bottom plate and no lower gasket and didn't pay enough attention to catch it. I kept all the parts old and new and once I got it down and really started looking it was pretty obvious. I put it back together with the old gasket and now about 7+ psi at idle versus barely moving the needle. I suspect at mid range it wasn't building quite enough pressure to open the poppet and the thermostats couldn't keep up with the heat load,,,,,,,,,,FYI, shit happens, don't assume anything and look at least twice

Engines using the 89984 impeller series (96148A8 water pump kit, for example) may experience elevated water pressure with a FRESH PUMP (at idle). Don't sweat this... it WILL tame down after a few trips to the lake. Perfectly normal.

Glad you found the gasket problem.... I was actually planning to send you there this morning (torn or damaged gaskets BELOW the impeller plate will ALMOST ALWAYS result in mid-range RPM overheating). This is due to aeration of the supply water to the pump.

Poppet valve functions on WATER PRESSURE. On this engine, the spring provides (approximately) 7.5 psi tension. As pressure exceeds the spring tension, the valve opens. With a brand-new (fresh) water pump, you can actually observe the CYCLING of the poppet valve (raise your RPM's slightly, in forward gear... perhaps 1100-1800 RPM's, and watch the water pressure gauge). You'll see pressure build, and then drop... build, and then drop (you're actually seeing the poppet valve opening and closing).

At IDLE, the poppet valve is CLOSED. Water flow is controlled by the thermostats.

As RPM's (and subsequently, water pressure) increase, the poppet valve opens, allowing a straight-through flow of water (which dumps to the adapter plate).

[dazy_cutter_45]

Thanks Don. I thought at some point a visible drop in water pressure should be seen, if I understood how the poppet system worked, I just didn't know at what pressure. Once I really looked at how the water flowed thru the plate and looked at my gaskets,,,,,what a DA. Thanks again for all you do

[dazy_cutter_45]

4#s at idle, slightly noticeable when the poppet cycles and no horn. So far so good, thanks again

[EuropeanAM]

Glad to hear it.

[per arne hansen]

Engines using the 89984 impeller series (96148A8 water pump kit, for example) may experience elevated water pressure with a FRESH PUMP (at idle). Don't sweat this... it WILL tame down after a few trips to the lake. Perfectly normal.

Glad you found the gasket problem.... I was actually planning to send you there this morning (torn or damaged gaskets BELOW the impeller plate will ALMOST ALWAYS result in mid-range RPM overheating). This is due to aeration of the supply water to the pump.

Poppet valve functions on WATER PRESSURE. On this engine, the spring provides (approximately) 7.5 psi tension. As pressure exceeds the spring tension, the valve opens. With a brand-new (fresh) water pump, you can actually observe the CYCLING of the poppet valve (raise your RPM's slightly, in forward gear... perhaps 1100-1800 RPM's, and watch the water pressure gauge). You'll see pressure build, and then drop... build, and then drop (you're actually seeing the poppet valve opening and closing).

At IDLE, the poppet valve is CLOSED. Water flow is controlled by the thermostats.

As RPM's (and subsequently, water pressure) increase, the poppet valve opens, allowing a straight-through flow of water (which dumps to the adapter plate).

Do the poppet valve lead water away from engine and into exos (adapter plate) ?

[EuropeanAM]

Do the poppet valve lead water away from engine and into exos (adapter plate) ?

The poppet valve opens and dumps water to the adapter plate/exhaust area, AFTER it has passed through the engine block.