Mercury 225-HP OptiMax: Cooling System Leak Under Cowling

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  Mercury 225-HP OptiMax: Cooling System Leak Under Cowling

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Author Topic:   Mercury 225-HP OptiMax: Cooling System Leak Under Cowling

humboldt jim posted 05-17-2010 09:29 AM ET (US)
[A] strange event [occured] yesterday that needs diagnosis: my [Mercury 225-HP OptiMax engine cowling] filled with water while running. A warning horn sounded, and when I turned to look, water was leaking out from under the cowling. I lifted the cowling and sure enough my engine was filled with saltwater. Water was spraying out of my [cooling system aspirator nozzle] at a usual volume, so I had no sense the problem was occurring prior to the warning signal. I ran the engine back to the dock, observing no leak. At home, runnig the engine in a tank, I noticed no water leaking either. I sprayed it down entirely with DPI after a freshwater rinse, and am now waiting a call back from mechanic. I did notice a long, thin, hex-head bolt, half-threaded, sitting, laying in the bottom of the engine [pan or lower cowling], and [I] wonder if that is the root cause. Any ideas what could cause this, please advise. Thanks
L H G posted 05-17-2010 02:31 PM ET (US)
Sounds like a blown out poppet valve.
weekendwarrior posted 05-17-2010 04:42 PM ET (US)
Maybe there is a gasket leaking, but only at higher pressures that you get when running faster. Maybe take [the boat out in] freshwater, remove the cowling, have someone else drive faster and faster, until you see the leak.
jimh posted 05-17-2010 08:45 PM ET (US)
The most likely source of the water under the cowling is from a leak in the cooling system. The suggestion to search visually for the source of the leak is probably the best method to locate the leak. An option might be to thoroughly rinse the power head, then return to operating in saltwater. Run the engine until the leak occurs, then look for a stain of evaporated salt as a sign of the source of the leak.
jimh posted 05-17-2010 08:46 PM ET (US)
The sounding of the warning horn may be significant. What was the meaning of the warning horn? Generally the cadence of the horn has to be interpreted to discover the meaning. Was the warning horn indicating an engine overheat condition?
RevengeFamily posted 05-17-2010 09:17 PM ET (US)
LHG is correct...
This happened to my 1999 Mercury Optimax 225.
The poppet valve helps control large volumes of coolant. It has a diaphram. That diaphram probably has a rip in it.
The poppet valve only opens when running the engine hard. I only found my leak when I ran the engine at least 3000rpm. The water is leaking through the torn diaphram and filling your lower pan.
To get back to the dock, I removed the rubber screw cover on the lower portion of the port side cowling. The open hole acted like a drain and allowed me to get home without salt water soaking the lower ignition coils and wires. (cylinders 5-6)
The poppet is located down low on the starboard side of the engine block. To get to it you'll have to remove the two (left and right) lower cowling pans. It's not a difficult fix.
Norm
humboldt jim posted 05-17-2010 09:37 PM ET (US)
The boat is at the shop and I'll take this information to my mechanic. I'll report out once we figure it out and thanks for your help.
jimh posted 05-18-2010 09:09 AM ET (US)
A rubber diaphragm in a poppet valve (or pressure-operated valve) must be under some sort of metal cover. I can't imagine that a rubber diaphragm that held back the pressurized cooling water would be able to leak directly into the cowling. I'd suspect a gasket has let go or a metal cover has corroded through.
Larry does have extensive experience with what breaks on Mercury engines. He's probably right-on with this diagnosis.
humboldt jim posted 05-18-2010 12:51 PM ET (US)
Just got word from the mechanic and it is the poppet valve. Quick and easy fix. Thanks for steering me in the right direction.
RevengeFamily posted 05-18-2010 04:42 PM ET (US)
Your correct Jim. The backing plate has slots cut into it. This is where the water will leak from after coming through the diaphram.
The repair kit I purchased came with the a new plate, diaphram and a gasket.
Norm
tedious posted 05-18-2010 04:49 PM ET (US)
Thinking about it, I guess it makes sense that the "other side" of a pressure actuated valve would need to be open to the atmosphere.
Tim
jimh posted 05-18-2010 09:02 PM ET (US)
"...a pressure actuated valve would need to be open to the atmosphere"--Only if the valve is regulated by atmospheric pressure. In the case of a poppet valve I believe the controlling pressure is supplied by a spring.
Litey posted 08-28-2014 11:21 AM ET (US)
Well I have the same problem ...Poppit valve ..
soaked my two lower coil packs and plugs ..
unfortunately ...I have had this happen a few times until I figured it all out ...
So...what should I do now other than replace the poppit
valve ?
I guess wash/spray it down with fresh water to remove the salt ...then what
? 1. remove the coil packs and clean connections ?
2. new plug wires
Anything else ?

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Author	Topic: Mercury 225-HP OptiMax: Cooling System Leak Under Cowling
humboldt jim	posted 05-17-2010 09:29 AM ET (US) [A] strange event [occured] yesterday that needs diagnosis: my [Mercury 225-HP OptiMax engine cowling] filled with water while running. A warning horn sounded, and when I turned to look, water was leaking out from under the cowling. I lifted the cowling and sure enough my engine was filled with saltwater. Water was spraying out of my [cooling system aspirator nozzle] at a usual volume, so I had no sense the problem was occurring prior to the warning signal. I ran the engine back to the dock, observing no leak. At home, runnig the engine in a tank, I noticed no water leaking either. I sprayed it down entirely with DPI after a freshwater rinse, and am now waiting a call back from mechanic. I did notice a long, thin, hex-head bolt, half-threaded, sitting, laying in the bottom of the engine [pan or lower cowling], and [I] wonder if that is the root cause. Any ideas what could cause this, please advise. Thanks
L H G	posted 05-17-2010 02:31 PM ET (US) Sounds like a blown out poppet valve.
weekendwarrior	posted 05-17-2010 04:42 PM ET (US) Maybe there is a gasket leaking, but only at higher pressures that you get when running faster. Maybe take [the boat out in] freshwater, remove the cowling, have someone else drive faster and faster, until you see the leak.
jimh	posted 05-17-2010 08:45 PM ET (US) The most likely source of the water under the cowling is from a leak in the cooling system. The suggestion to search visually for the source of the leak is probably the best method to locate the leak. An option might be to thoroughly rinse the power head, then return to operating in saltwater. Run the engine until the leak occurs, then look for a stain of evaporated salt as a sign of the source of the leak.
jimh	posted 05-17-2010 08:46 PM ET (US) The sounding of the warning horn may be significant. What was the meaning of the warning horn? Generally the cadence of the horn has to be interpreted to discover the meaning. Was the warning horn indicating an engine overheat condition?
RevengeFamily	posted 05-17-2010 09:17 PM ET (US) LHG is correct... This happened to my 1999 Mercury Optimax 225. The poppet valve helps control large volumes of coolant. It has a diaphram. That diaphram probably has a rip in it. The poppet valve only opens when running the engine hard. I only found my leak when I ran the engine at least 3000rpm. The water is leaking through the torn diaphram and filling your lower pan. To get back to the dock, I removed the rubber screw cover on the lower portion of the port side cowling. The open hole acted like a drain and allowed me to get home without salt water soaking the lower ignition coils and wires. (cylinders 5-6) The poppet is located down low on the starboard side of the engine block. To get to it you'll have to remove the two (left and right) lower cowling pans. It's not a difficult fix. Norm
humboldt jim	posted 05-17-2010 09:37 PM ET (US) The boat is at the shop and I'll take this information to my mechanic. I'll report out once we figure it out and thanks for your help.
jimh	posted 05-18-2010 09:09 AM ET (US) A rubber diaphragm in a poppet valve (or pressure-operated valve) must be under some sort of metal cover. I can't imagine that a rubber diaphragm that held back the pressurized cooling water would be able to leak directly into the cowling. I'd suspect a gasket has let go or a metal cover has corroded through. Larry does have extensive experience with what breaks on Mercury engines. He's probably right-on with this diagnosis.
humboldt jim	posted 05-18-2010 12:51 PM ET (US) Just got word from the mechanic and it is the poppet valve. Quick and easy fix. Thanks for steering me in the right direction.
RevengeFamily	posted 05-18-2010 04:42 PM ET (US) Your correct Jim. The backing plate has slots cut into it. This is where the water will leak from after coming through the diaphram. The repair kit I purchased came with the a new plate, diaphram and a gasket. Norm
tedious	posted 05-18-2010 04:49 PM ET (US) Thinking about it, I guess it makes sense that the "other side" of a pressure actuated valve would need to be open to the atmosphere. Tim
jimh	posted 05-18-2010 09:02 PM ET (US) "...a pressure actuated valve would need to be open to the atmosphere"--Only if the valve is regulated by atmospheric pressure. In the case of a poppet valve I believe the controlling pressure is supplied by a spring.
Litey	posted 08-28-2014 11:21 AM ET (US) Well I have the same problem ...Poppit valve .. soaked my two lower coil packs and plugs .. unfortunately ...I have had this happen a few times until I figured it all out ... So...what should I do now other than replace the poppit valve ? I guess wash/spray it down with fresh water to remove the salt ...then what ? 1. remove the coil packs and clean connections ? 2. new plug wires Anything else ?