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Subject: TWL: Exhaust overheat alarm sensor location on Lehman 120s
From: Rich Gano (rgano@XXX.XXX)
Date: Wed May 01 2002 - 17:52:50 EDT
I recently mounted 160 degrees F alarm sensors (from Doc
Freeman Marine) on the exhaust elbows of my two Lehmans and
Onan generator, and the one on the stbd engine went off
Sunday while at "battle speed" of 2100 RPM. My normal
operating range is 1600-1800 rpm, and I have had no alarms
in that operating range. Luckily wife was below to hear the
bell because I could not hear it from the FB. That problem
was corrected last night with an additional alarm buzzer on
the FB. Had tried listening to the bell at the lower
station pier side without wind and crashing bow wave, and it
seemed loud enough then.
After being notified of the alarm, I shut down the engine
and found no obvious fault (all fluids ok and engine temp
gauge never exceeded 180F). Restarted, checked cooling
water flow at stern, and ran at moderate speed of 1200 rpm
for a few minutes until alarm light went out. Ran at 1900
and then at 2000 rpm for awhile with no alarm. As soon as I
pushed to 2100, the alarm went off. NOW I noticed that the
stbd engine's sensor was mounted ALONGSIDE the raw water
inlet on the exhaust elbow instead of OPPOSITE the inlet, as
had been done on the port engine. Water hitting the
opposite wall of the exhaust elbow makes a big difference in
temperature.
Loosening the sensor's mounting clamp and rotating it to the
other side of the elbow seems to have solved the problem of
premature alarming. Nice to have had an op test without a
Joe Engel type consequence. Luckily the wiring tube to the
FB had enough room for another twinned wire for the second
alarm buzzer. Otherwise it's an all-day sucker of
disassembly/reassembly to get any more wire runs up there.
Rich Gano
CALYPSO (GB42-295)
Homeport Southport, FL
I'd rather be cruisin'
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