1993 200hp Mercury poppet valve leaking thru weep hole

stclarl_98

Recruit
Joined
Aug 18, 2016
Messages
3
There are many confusing answers to the purpose of this mechanical poppet valve and why water would flow out of the weep hole. I have read them all and have formulated my own idea as why this "weep hole" leak is happening and the purpose of the poppet valve. Here is my conclusion on my motor but the theory is the same for yours. Replace your water pump.

POPPET VALVES SHOULD NEVER LEAK UNDER NORMAL OPERATION OF ANY BOAT MOTOR... PERIOD. (Study the attached water flow diagram to follow along)

Now lets consider normal operation/ ideal running condition.

The normal water pump pressure for boat motors varies between 5 - 12 psi (what is it for yours?)

When we initially start the boat motor, the thermostats are closed and water will NOT show at the "tell tale" nozzle. (the little tube that spits water out of the cowl)
As the motor temperature increases, the thermostats open, and the water flows out of the "tell tale" nozzle. :) (my own personal warm and fuzzy moment when boating offshore)

It may spit at the beginning but as the thermostats open and the motor warms up, the water stream should be steady.
At idle, you might even see the "tell tale" flow shut off as the thermostats close again but when at higher RPM it should be a solid steady stream not just a spit.

The poppet valve is designed to open from "normal" water pump pressure and forced out to prevent water leaking thru the weep hole. If the water pump is faulty and not maintaining 12 psi, there is NOT enough pressure to push open the poppet valve and the lower flow of water from the top of the block feed hose will be the water that leaks out the weep hole.

In the diagram, water is pushed up from the water pump to circulate throughout the water jacket. Because the motor was just started the thermostats will be closed and we have a "closed loop system" therefore the only place the water can exit is thru the poppet valve into the exhaust ports. Now in my motor the diagram shows one of the feeds (little square to the right of the poppet in the diagram) coming from the top of the block to the poppet. This by the way is the only tube you see feeding the poppet valve on my motor the other feeds are internal to the water jacket. The water flow from this tubing has a second path thru the two plates (and a hole in the gasket) of the poppet valve and out the weep hole if the poppet valve is not forced out internally by the necessary pressure created by THE WATER PUMP.

 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,047
The hole in the cover is an AIR VENT and allows the diaphragm to move.-----If water leaks out that vent hole there is a problem with the diaphragm or the sealing / gaskets of the housing.
 
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