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mercury lower
- Thread starter Oldman
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READ THIS OLDMAN
1997 Mercury 200 EFI water pressure/temp alarm
Originally posted by jwolfe73 View Post
I took my boat out last fall and the water pressure alarm went off and I noticed that there wasnt any stream out the back of the motor. I have just replaced the water pump but I didnt notice anything wrong with the old one. I havent fired it up yet to see if I get the stream of water but I wanted to check to see if there is something else I might look at while I have it apart?
If there is no telltale stream of water you need to proceed with caution. No cooling can mean destroyed motor.
I had no telltale on my motor once, but it seemed to be cooling just fine. That one turned out to be a plugged telltale fitting. Cleaned that out and had good telltale.
But...
I was having an intermittent alarm on a 2002 200HP Mercury Smartcraft EFI outboard. Sometimes on heavy acceleration or even regular acceleration I would get an alarm and I would have to throttle back to below 1000 RPM and the alarm would clear. I would accelerate and things were fine.
This spring I picked up a SmartCraft System Monitor and hooked it up so I could get a handle on this. Best investment I have made in a long time.
So the System Monitor gauge was indicating a low water pressure alarm. So I did some research here on the Hull Truth (that's to ALL tips) and came upon a thread that suggested maybe stuck thermostats and/or poppit valve.
Went to check them out and noticed the thin grey water pressure line. Comes from the bottom of the block near the flush tube. That's when the penny dropped and a few other things all fit into place. When I first put this motor on I never hooked up the grey water pressure line and it was spewing water out the front, but things worked fine so I didn't really think much about it. Pissed into the motor well, no issue. Right?
Anyway, I took out the hose flush plug on the back of the motor and it was fill of fine sane sediment. Not a huge surprise as there are a few lakes where launch and pull out are from sand beaches. Got me thinking, what if the small grey hose is plugged too, right where it comes out of the block. Hmmm... come to think of it, I haven't seen water pissing out of the unconnected grey tube for a long time. Forgot all about it.
The grey tube has 3 connections on my motor, one I left unconnected, one to the block and the last to what appears to be a sensor up high on the block in a plastic bracket. So I disconnected it at the sensor and blew into it and I could hear air come out of the unconnected end in the motor well. Tube was clear.
Unscrewed the fitting from the block for that grey tube. Aha... There was a little piece of rotten wood stuck in the fitting. Never would have come out with any amount of flushing.
I realize now that leaving the tube open in the motor well is bad for multiple reasons. First, it will lower the pressure that the water pressure sensor reads since the tube never properly pressurizes when the tube is open. Second, having the tube open let water flow continuous which makes it more likely that debris will go into the tube. If the tube simply pressurizes as normal, very little water actually flows into that tube, just enough to compress any air in the tube, and when the water pressure reduces, the back flow will probably flush the debris back out if any went in. But with the tube open, the outward continuous flow allows debris to go into the tube and with no reverse flow when the pressure lowers, there is nothing to flush the debris back out.
While I had that grey tube fitting off I hooked up the garden hose to the flush fitting and gave it a good flush to get rid of any sand and debris as well.
I haven't had a chance to water test the unit since doing this but I am pretty certain this was the cause of my alarm.
1997 Mercury 200 EFI water pressure/temp alarm
Originally posted by jwolfe73 View Post
I took my boat out last fall and the water pressure alarm went off and I noticed that there wasnt any stream out the back of the motor. I have just replaced the water pump but I didnt notice anything wrong with the old one. I havent fired it up yet to see if I get the stream of water but I wanted to check to see if there is something else I might look at while I have it apart?
If there is no telltale stream of water you need to proceed with caution. No cooling can mean destroyed motor.
I had no telltale on my motor once, but it seemed to be cooling just fine. That one turned out to be a plugged telltale fitting. Cleaned that out and had good telltale.
But...
I was having an intermittent alarm on a 2002 200HP Mercury Smartcraft EFI outboard. Sometimes on heavy acceleration or even regular acceleration I would get an alarm and I would have to throttle back to below 1000 RPM and the alarm would clear. I would accelerate and things were fine.
This spring I picked up a SmartCraft System Monitor and hooked it up so I could get a handle on this. Best investment I have made in a long time.
So the System Monitor gauge was indicating a low water pressure alarm. So I did some research here on the Hull Truth (that's to ALL tips) and came upon a thread that suggested maybe stuck thermostats and/or poppit valve.
Went to check them out and noticed the thin grey water pressure line. Comes from the bottom of the block near the flush tube. That's when the penny dropped and a few other things all fit into place. When I first put this motor on I never hooked up the grey water pressure line and it was spewing water out the front, but things worked fine so I didn't really think much about it. Pissed into the motor well, no issue. Right?
Anyway, I took out the hose flush plug on the back of the motor and it was fill of fine sane sediment. Not a huge surprise as there are a few lakes where launch and pull out are from sand beaches. Got me thinking, what if the small grey hose is plugged too, right where it comes out of the block. Hmmm... come to think of it, I haven't seen water pissing out of the unconnected grey tube for a long time. Forgot all about it.
The grey tube has 3 connections on my motor, one I left unconnected, one to the block and the last to what appears to be a sensor up high on the block in a plastic bracket. So I disconnected it at the sensor and blew into it and I could hear air come out of the unconnected end in the motor well. Tube was clear.
Unscrewed the fitting from the block for that grey tube. Aha... There was a little piece of rotten wood stuck in the fitting. Never would have come out with any amount of flushing.
I realize now that leaving the tube open in the motor well is bad for multiple reasons. First, it will lower the pressure that the water pressure sensor reads since the tube never properly pressurizes when the tube is open. Second, having the tube open let water flow continuous which makes it more likely that debris will go into the tube. If the tube simply pressurizes as normal, very little water actually flows into that tube, just enough to compress any air in the tube, and when the water pressure reduces, the back flow will probably flush the debris back out if any went in. But with the tube open, the outward continuous flow allows debris to go into the tube and with no reverse flow when the pressure lowers, there is nothing to flush the debris back out.
While I had that grey tube fitting off I hooked up the garden hose to the flush fitting and gave it a good flush to get rid of any sand and debris as well.
I haven't had a chance to water test the unit since doing this but I am pretty certain this was the cause of my alarm.
