200 Hp Poppet Valve / Water Pressure

[thinback]

I have 1987 Mercury 200 hp thats been rebuilt and stock except for a bobs nose cone. I recently purchased this motor late in the summer and is in good condition. When I finally got a chance to try it out, the water pressure was maybe 5 lbs. I replaced the water pump and I have plenty of water coming from the tell tale and the thermostats are opening properly. I searched the web site and found some other people with similar problems that could of been the poppet valve. My motor has a poppet valve cover that looks like a small and large circle connected with a hose fitting coming off of the small circle that goes to the top of the engine block. The valve looks like its in new condition and it isn't stuck.
The orfice in the engine block behind the flange where the hose is connected is plugged with marine tex. Could this be the cause of the low water pressure? What would the benifit be to plugging this orfice? I'm new to v-6 mercury engins. I did race 2 cylinder outboard motors for many years but they didn't have poppet valves or thermostats Any thoughts or suggestions would be appreciated
Thanks

[j_martin]

I've been helped before. Check out the diagram in reply #7

http://forums.screamandfly.com/forums/showthread.php?t=118236

[Fish]

I've been helped before. Check out the diagram in reply #7

http://forums.screamandfly.com/forums/showthread.php?t=118236

That was a picture I posted a while ago, guess reese downloaded it even though it has nothing to do with politics ;). I beleive it is for a 1989 and newer motor, yours in a 1987. I am not sure if there is a difference in the cooling system or not between the two. Hopefully someone will come along with the answer, if not, you might try sending a pm to US1 (john marles).

[j_martin]

That was a picture I posted a while ago, guess reese downloaded it even though it has nothing to do with politics ;). I beleive it is for a 1989 and newer motor, yours in a 1987. I am not sure if there is a difference in the cooling system or not between the two. Hopefully someone will come along with the answer, if not, you might try sending a pm to US1 (john marles).

Mine's a 88 XR4. The diagram seems right to me, and explained some things I didn't understand.

Are you sure the pressure gauge is hooked up to the right hole? Might seem like a dumb question, but we just went through a whole thread to find out the pressure gauge was hooked up to the telltale hose.

The pressure can be pretty low, and still be normal at idle, as long as it's cool and you get a telltale stream. Part way up (I think about 3000 rpm,) the pressure in the block should open the poppet valve at around 12 PSI. If you're sure it's hooked up so you are actually looking at block water pressure, you should be able to figure out what's happening by watching the pressure change or not as you go through the rpm range. When you take in some of the lake bottom, or totally blow an impeller into the works, sometimes one or more of the water passages will plug up and give trouble.


Hope it helps
John

[Fish]

cool, thanks.

[nik kurdziel]

5lbs @ w.o.t. or idle?

[j_martin]

That little hole that is plugged goes (through a passage in the block) to the hose that goes to the top of the diagram, to the water inlet. I think is is a control pressure for the poppet valve. I suspect that if the hole is plugged, it could be erratic, or wrong pressure.

hope it helps
John

[j_martin]

See What I mean.

http://forums.screamandfly.com/forums/showthread.php?t=120416

[thinback]

It goes up to five pounds then drops down to maybe two at crusing speed. I don't have a water temp guage on the boat now it didn't seem to over heat. The motor had a fitting for the water pressure on the tell tale hose. It sounds like that may be a problem. Where should the water pressure guage be plumbed to the block? and where do I plumb the water temp gauge? Thanks for everyones feedback
Bill

[j_martin]

There's a threaded hole in the top of the block, probably has a plug in it now. That's where it goes.

I think you'll find that the water pressure is just fine.

John

[nik kurdziel]

My temp sender is in hole on the front face of the cyl.head. {Facing rear of motor, on the top left side.}
There is also one on the right side,I think that's is for the alarm sender. There are some pretty sharp people on this site that can either verify this or correct me on it.{the right side info}

[us1]

Is that a one piece exhaust adapter?

[j_martin]

I think those are blind holes for head temp sensors. Look on the top of the engine for a threaded hole between the cylinder banks.

[THE FAST ONE]

<TABLE id=HB_Mail_Container height="100%" cellSpacing=0 cellPadding=0 width="100%" border=0 UNSELECTABLE="on"><TBODY><TR height="100%" UNSELECTABLE="on" width="100%"><TD id=HB_Focus_Element vAlign=top width="100%" background="" height=250 UNSELECTABLE="off">IF NOT WHERE J.MARTIN SAID,IN LAST POST ,SHOULD BE ON TOP OF BLOCK WITH A TEE,COMING OFF HOSE,THAT IS BACK TO BIG PLUG IN TOP OF BLOCK,FISHING MOTOR'S ALL READ SAME PRESSURE,THERE OR EHAUST DIVIDER PLATE TOP MIDDLE HOLE,I HAVE RAN TWO PRESSURE GUAGE'S EACH LOCATION AT SAME TIME,TO VERIFY. RIGHT OR STARBOARD HEAD IS FOR TEMP GUAGE ON FISHING MOTOR--ED</TD></TR><TR UNSELECTABLE="on" hb_tag="1"><TD style="FONT-SIZE: 1pt" height=1 UNSELECTABLE="on">

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I think those are blind holes for head temp sensors. Look on the top of the engine for a threaded hole between the cylinder banks.