Poppet Valve

FreeBeeTony

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Can someone tell me the function of a poppet valve on a 1998 225 Johnson?

I am an I/O guy......looks like a thermostat bypass of some sort to me.

A friend of mine is replacing his head gaskets and cleaning the water passages.

we are trying to understand the water flow.

Any insight would be appreciated.
 

bob johnson

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Re: Poppet Valve

I think it is basically a relase valve for bypassing the thermostat (that has closed off the heads from water coolant,) when the water pressure reaches a certain amount. Or if the thermostat is open to allow more coolant flow.

thats my guess.. on my motors the whole thermostat unit is under spring pressure and is a "poppet valve" defacto

bob
 

durban

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Re: Poppet Valve

the poppet valves are spring operated k , as the motor starts the impeller sucks water pushing it into the motor , that water has to go some where , next to the poppet valves is the therm-st k, when the motor is cold & the water has not reached temp & the therm-st is still closed , the pressure builds up pushes the poppet valves up, the spring compresses the valve opens up & the water goes out , also when the motor has reached temp the stat opens but does not handle the amount of volume that the impeller pumps when the rpm increases , that extra volume of water then goes out through the poppet valves & then out the exhaust . the whole idea to put the poppet valves there is to keep the water in the motor until it warms up , so if you start your motor & SUDDENLY take off the rpm picks up , more volume of water , its got to go some where , cause the pressure builds up, now remember you did not give the motor time to warm up for the thermostat to open up k if you gonna do that , poppet valves open water out & bobs your uncle , cheers m8t
what you can do is fit a **** hole in the thermostat cover , then when you see the water coming out , then you know your motor has warmed up , cause the thermostat has opened , then you ready to go.& at the same time it tells you the thermostat is working , cause you cannot see it opening .the water coming out , den you know for sure its working
 

Faztbullet

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Re: Poppet Valve

The "poppet" on this engine is to release excess water pressure. It is dumped into the cylinder heads at the t-stat covers. The V-6 looper heads run nearly dry with the only cooling is from the t-stat reliefs and opening of t-stat, thus the reason they are hot to the touch...when poppet opens the excess water is dumped into t-stat covers and helps cool the heads. Do not drill anything on the covers as this will effect cooling......
 

Haffiman

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Re: Poppet Valve

Evinrude/Johnson engines only uses thermostat function on low rpm to keep temp up. This to ensure proper combustion and a bit cleaner engine. At higher rpm's, they try to let the engine run as cool as possible, and they may 'enrich' the fuel mixture similar when pulling the choke on a cold engine. This gives more fuel burned at higher rpm which gives more HP in the same cylinder volume. The poppet valve simply by-passes the thermostat with cooling water. On some engines a mechanical valve on the throttle arm, on some all operated by waterpump pressure. Note that a worn out impeller might need a higher rpm to obtain the needed pressure which may totally mess up the mixture leaving some engines running far too rich at high rpm's.
 

durban

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Re: Poppet Valve

The "poppet" on this engine is to release excess water pressure. It is dumped into the cylinder heads at the t-stat covers. The V-6 looper heads run nearly dry with the only cooling is from the t-stat reliefs and opening of t-stat, thus the reason they are hot to the touch...when poppet opens the excess water is dumped into t-stat covers and helps cool the heads. Do not drill anything on the covers as this will effect cooling......

i do understand what you are saying about do not" DRILL". However from 1972 to 1986 , 65hp , 70hp, & 75hp all the cylinder head cover,s were made the same , what happens when the thermostat opens the hot goes to the left through the hole in the cover ,[ take cover off where the thermostat is you will see the hole ] the poppet valve water goes through into the cylinder head cover were the bridge is [ you will see it at the bottom poppet valve ] the water merges , because the water from the thermostat goes to the left & poppet valve water doesn't go into the little chamber where the thermostat is , cause its bridged there with a gasket in between , now my conclusion ive come to . iam gonna drill the hole , & , whether you drill the hole or not the water still gets in to the cylinder head cover ,over the bridge by the poppet valves , got my head spinning now , my advantage , i know when my motor is hot enough to go & i know the thermostat is working . observing the ****
 

Haffiman

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Re: Poppet Valve

Durban: You know the thermostat is working just by observing the amount of water coming out the exhaust relief holes on the leg, no need for any 'fancy' solutions. At low idle, rpm below poppet relief pressure rpm, water will go out the relief holes as thermostat opens, almost stops when closed.
 

durban

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Re: Poppet Valve

you can , but when iam at the controls & the sea a little bit rough i dont wan to run back wards & forwards from the controls to go & have a look , easy for me to stay at the controls & just turn my head , we try any way k, will keep you up to date , cheers
 

Faztbullet

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Re: Poppet Valve

i do understand what you are saying about do not" DRILL". However from 1972 to 1986 , 65hp , 70hp, & 75hp all the cylinder head cover,s were made the same ,
This is a V-6 and water does not circulate like the older 3 cylinder engines........
 

durban

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Re: Poppet Valve

OK , so i can put up a thread ,that you can drill a hole in the cover that covers the thermostat & put a **** tube there ,i have all ready done this & it works , have a look
 

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Haffiman

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Re: Poppet Valve

I think I would just prefer a simple dual function temp and pressure sensor with Blue Ray. Then my cell just calls me up if anything goes wrong. Better than having an engine pissing out water in all directions and different purposes.
 

bob johnson

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Re: Poppet Valve

thats nice, but what does that have to do with a poppet valve?

The op just wants a lesson in the purpose of a poppet valve on a V6 engine.

is your pizzer tube an exercise in knowing if the thermostat is opening and how much flow it is allowing?
the motor already has a tell tale...so what is the purpose you are trying to acheive with putting another in the head ?

I have a 1988 70 hp ....if its a worthwhile exercise, maybe ill do it!!!

bob
 

Haffiman

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Re: Poppet Valve

The probably best additional safety alarm/warning you may add to what is already on the engine from the factory (Tell-tale and temp alarm), would be an exhaust temp alarm switch that sends you to slow when engine starts to run lean and before pistons melts down. That however might be a bit over the edge. The 'poppet valve' works different on different engines as I mentioned above, the engine in question, a V6, is not even close to the 3 cyl engines in design.
It has both a poppet valve and pressure regulated flow to the thermostats. In short, when the poppet valve opens, it looses the water-pressure holding the thermostats, the thermostats gets pushed off and cooling increased. If you hook up a temp gauge, you may notice that the engine temp actually DROPS at a certain rpm/pressure. To be sure it balance correct with rpm and load, impeller must be changed about every second year and do NOT overprop the engine!!
 

durban

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Re: Poppet Valve

I think I would just prefer a simple dual function temp and pressure sensor with Blue Ray. Then my cell just calls me up if anything goes wrong. Better than having an engine pissing out water in all directions and different purposes.

when i can afford one i will get it , for now i do what suits my pocket .
 

durban

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Re: Poppet Valve

the point iam trying to make & get the message through i have a motor , the water was pissing fine every thing looked sweet , then one day it cooked , & had to radio coast guard ,the water was not coming to the thermostat , so this time iam gonna do it my way , by putting the hole where i can see its pissing water when the thermostat opens then i also know its working, have a look here this was the cause , holes in the exhaust manifold plate the water was going out the exhaust

http://forums.iboats.com/showthread.php?t=532243
 

Haffiman

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Re: Poppet Valve

the point iam trying to make & get the message through i have a motor , the water was pissing fine every thing looked sweet , then one day it cooked , & had to radio coast guard ,the water was not coming to the thermostat , so this time iam gonna do it my way , by putting the hole where i can see its pissing water when the thermostat opens then i also know its working, have a look here this was the cause , holes in the exhaust manifold plate the water was going out the exhaust

http://forums.iboats.com/showthread.php?t=532243

After having been in the marine engine industry for some 30+ years, I sold my dealership back in 2004 and went sailing around the world. I had a couple of options: Buying a 40+ boat second hand or buy my 37 Jeanneau brand new. As I was going to be in the middle of 'no-one to call', I decided to go for e new boat Old boats breaks sooner, new boats hopefully lasts a bit longer. I soon lost track of people with old and bigger boats with engine or whatever breakdowns on their way, more or less stranded.I managed to reach Malaysia without any serious trouble that was not fixable at sea. You are talking about a 40+ year old engine and seems to be a bit annoyed that it shows sign of corrosion and breaks down??? Rough design lifetime of a marine engine used in salt water is about 10 years. After that at about any time, gaskets may start leak, anti corrosion coatings (anodizing) may be gone etc. However manufacturers normally have some periodically service/maintenance tasks to be done at certain intervals. In general the time is more important than the running hours between these intervals. Had impeller/thermostat service been done according to those intervals on your engine from NEW, what you experienced may not have happened. Did you dismantle and reseal powerhead and gearbox every 10 years??
 

bob johnson

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Re: Poppet Valve

thats why a temperature guage is one of the most important tools to keep you from destroying your engine.....you would have still be een stuck probably, but you wouldnt have ruined your engine...you see the temp rise and rise and rise, and you TURN THE MOTOR OFF>..there disaster averted

bob
 

FreeBeeTony

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Re: Poppet Valve

I just asked about the poppet valve.......:)

I got my answer and it's kinda what I thought it was......

Carry on.
 

durban

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Re: Poppet Valve

the motor is about 40 years old when i got it ,went ok for a few months , when i buy any motors to play around with the first thing i do is strip it right down whether it in running order or not & then rebuild them this on of the things i do ,
http://forums.iboats.com/showthread.php?t=531964
 

Faztbullet

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Re: Poppet Valve

I have a 1988 70 hp ....if its a worth while exercise, maybe ill do it!!!
Sorry Bob but yours is the combo design as t-stat is in the poppet, dont drill it as you will lose the cooling to the external part of head.
 
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