Exhaust alarm

[neptune]

28 TE with 315 Yanmar. Rebuilt 300 hours ago.

I am getting an exhaust alarm. I think it is HOT exhaust alarm. Engine temp is ok, oil pressure ok, I can put my hand on the exhaust as it exits engine and its not hot. Engine sounds good, not hot smell.

Any ideas? Bad sensor?

[Norseman]

Cooling water flow, or lack off?

[carolmarie]

I experienced an incident similar to the one you describe with my 2001, 6LP-STE a few years ago. High alarm sounded at idle/low RPM but went away at higher speeds. Turned out to be an exhaust sensor in the raw water heat exchanger. It eroded over time and wasn’t working well at lower engine speeds. Try increasing the throttle and see if the alarm stops. Don.

[Tree]

Agreed. Sounds like the raw water flow sensor. They wear on the shaft - later engines had them deleted. Mine went the same way so I’ve disconnected it despite making the repairs the yanmar techs over here guided me with.

[neptune]

Its a 2000 6LP-STE Came from east coast so it was a salt water boat. Ive run the engine with alarm on for several hours now. No apparent problem. Alarm comes on instantly as I start engine. So how could exhaust be hot, etc. I think sensor. Where is the raw water sensor?

[Carl]

In the document library there are the parts manual and maintenance manual with exploded views of your Yanmar. I’m sure it’s in there.

[Tree]

Its a 2000 6LP-STE Came from east coast so it was a salt water boat. Ive run the engine with alarm on for several hours now. No apparent problem. Alarm comes on instantly as I start engine. So how could exhaust be hot, etc. I think sensor. Where is the raw water sensor?

Raw water sensor is square headed with cables coming out of it, just upstream of the intercooler zinc. It’s right on the top you can’t miss it. I think it’s either 3/4 or 7/8” A/F spanner to undo. You’ll find the shaft is worn and the float jams on the shaft making the engine think no water is getting through. They’re about £180 to replace over here but you can repair them using some heat shrink and two part epoxy to fill the gap.

[carolmarie]

Here’s a photo that shows you what Tree was saying.
Also, have you rev’d the engine to say, 2500 RPM and did the alarm stop? Don

2E9E55D4-DBFA-4E6A-8E7A-9EBFDAC48067.jpeg

[Yearwood]

Yes it is caused by a faulty water flow alarm which is labeled "exhaust temperature" on the alarm panel. Water flow causes a sensor to ride up a plastic shaft. Over time the shaft erodes and the sensor hangs up. It was a simple replacement. However, Yanmar has now redesigned the sensor to eliminate the plastic in place of bronze and the unit is self grounding with only one wire coming out of it to be connected to the blue/white wire to the alarm panel. The other wire can be dead ended.

[neptune]

Thanks, Ive run the engine for hours without an issue. Yes I ran it up well over 2,500RPMs and no change. Its got to be the sensor.

[Yearwood]

I would replace it. If there is a failure of flow due e.g. to a broken hose it will go off immediately. It is a good alarm albeit completely mislabeled
.

[neptune]

After m much concern etc., I located the sensor and found two wire connectors a few inches away. I simply prodded with them a tad and alarm quit. Likely need a little electrical grease.

[nebulatech]

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