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Old 12-30-2016, 11:13 AM   #1
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lehman 120 alarms and senders need info

I'm refurbishing my 81 CT trawler, including the two Lehman 120's and the entire electrical set up, which gives the phrase "rats nest" an entirely new meaning. I've tracked all the gauge wiring and am replacing all of the gauges, but can someone help me source replacement alarm senders and units for the low oil pressure and high water temp alarms.

Also, are there other alarms that users recommend or have found useful to install - Bilge alarms, etc and where to source them.

Randy
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Old 12-30-2016, 11:50 AM   #2
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American Diesel or Bomac Marine will have the sending units.

We have an Aqua Alarm system on Hobo (single engine) and love it.

20003 Five Systems Monitoring Kit, Twin, with 5 Detectors & Bell [] - $599.00 : AQUALARM, Warning Systems For Land And Sea
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Old 12-30-2016, 12:02 PM   #3
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Install oil temp or oil pressure sender on your velvet drives. Either T off a fitting or use the plug next to the top rear fitting.
A high water alarm is a good idea. Use water witch above typical level of water in bilge.

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Old 12-30-2016, 01:00 PM   #4
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High water alarms for sure.

Then as others have mentioned raw water flow alarms for the main and genset. A flow alarm for the A/C raw water line is nice as well.
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Old 12-30-2016, 01:06 PM   #5
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I would use senders matched for the gauges.

Alarms are always a good choice...my new thrust is towards coolant flow....worried about low coolant (burst hose) or belt/pump failure.

Then the usual for the engine...oil,temp, volt...

I also have a raw water flow alarm.
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Old 12-30-2016, 01:25 PM   #6
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If you are buying new guages then you should be using the senders for those guages.
Some mismatched senders may work but maybe not. They are variable resistors and the resistance range has to match the guage other wise the guage may read but it will be wrong. Get the proper senders.

Low oil pressure alarms are usually simply a switch which for oil is normally closed and opens at something like 10 or 15psi. Usually a simple 1/8 or 1/4" NPT thread. Cole Hersey, Stewart Warner and others.

High temp are also normally open and when the temp reaches a setpoint then they close triggering the alarm. They have a probe that enters the water jacket so again need to be matched to what you have now. The thread will be larger, maybe 1/2NPT and the probe length matched.

As suggested American Diesel should be able to help or a good parts store if you take the existing units with you.

Usually the trip points, pressure and temps. are stamped or printed on the bodies but it may take removal to see. Often also the mfgr. brand which will help.

If you are on your own to find then a truck parts place may be more help than the typical auto parts store these days. Take the old with you.
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Old 12-31-2016, 04:18 PM   #7
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Thanks everyone. After suggestions here and additional research I'm going to add an aqualarm panel with temp alarm, oil pressure alarm, and exhaust temp alarm. Am ordering new gauges w senders and adding transmission oil gauge. Will add a raw water flow kit when I pull the boat and replace seacocks in a couple months.
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Old 01-01-2017, 06:16 AM   #8
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Quote:
Originally Posted by kazenza View Post
. . . I'm going to add an aqualarm panel with temp alarm, oil pressure alarm, and exhaust temp alarm.
You might want to consider getting Aqualarm's "alarm bell" option. The standard piezo buzzer can be hard to hear - especially if you are some distance from it.
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Old 01-01-2017, 07:04 AM   #9
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You might want to consider getting Aqualarm's "alarm bell" option. The standard piezo buzzer can be hard to hear - especially if you are some distance from it.
The bell will wake the dead. Even on the flybridge with the wind blowing, you hear it.
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Old 01-01-2017, 08:43 AM   #10
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Have you looked at vdo stuff? We use some of there stuff in gens. The oil psi and water temp have a normally open contact for an alarm or shutdown as well as the sending portion for the gauge. They work good if you're short on holes to put them in.
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Old 01-01-2017, 01:24 PM   #11
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I was wondering what the other contacts were for on the existing pressure and temp gauge senders. The Lehman 120s are already tapped for the extra switches so no problem using the switches that aqualarm sells for its panel, however I'm pretty sure I'm overpaying for standard cutout switches. I also have what looks like a generator cutout switch on each engine, but I'm not sure what that accomplishes. The bell is a good idea up top, even though I will have full alarms and panels top and bottom.
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Old 01-01-2017, 01:35 PM   #12
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see pdf page 27,28 for the senders/switches. if you have vdo senders now. you should be able to pull up the info on them.

http://www.usa.vdo.com/generator/www...redirect=false
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Old 01-02-2017, 08:23 AM   #13
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Quote:
Originally Posted by kazenza View Post
I was wondering what the other contacts were for on the existing pressure and temp gauge senders. The Lehman 120s are already tapped for the extra switches so no problem using the switches that aqualarm sells for its panel, however I'm pretty sure I'm overpaying for standard cutout switches. I also have what looks like a generator cutout switch on each engine, but I'm not sure what that accomplishes. The bell is a good idea up top, even though I will have full alarms and panels top and bottom.
Where on a Lehman 120 would one add an additional temp sender? There are two ports that I know of underneath (sort if) the expansion tank. One is used for engine temp, the other for the high temp alarm. I need TWO temp senders. Can I use the hole on the side of the expansion tank in which there is a pipe plug? And, yes, I know about dual station senders. Not an option I want to use.
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Old 01-02-2017, 09:01 AM   #14
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Aqualarm has a bolt on temp sensor that is attached under a head bolt.
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