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Beneteau F310 ~ APOTHIC
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Discussion Starter · #1 ·
I have a Yanmar YSB-8 engine on my 1977 CS27, which thankfully runs like a top. The engine panel, however, is in rough shape and due for a make-over.

As I understand it, the engine system has sensors for oil pressure, engine temperature, and voltage (off alternator). I'm wondering if the existing sensors can feed an analog gauge rather than the dummy lights they are currently connected to. If not, is there a moderately painless way to get this information in the right format? I am most interested in looking to have a temperature gauge and oil pressure gauge.

I also want to add a analog tachometer, but I believe that I have to have my alternator modified for a pickup before I can do this. (I don't like the look of the tiny-tach, which I think is my only alternative).

Would appreciate any guidance, as I don't have much information on how these work.

Thanks in advance,
Chris
 

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Generally the alarms use temperature and pressure switches, while gauges need sensors that vary in resistance. You would need to either add the sensors, or replace the switches with a unit that has both the switch and the variable resistance sensors built in. Most of the marine equipment vendors (West Marine, Defender, ect.) carry the sensors and gauges. Not too expensive - about $50 for a sensor/gauge set.
 

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One of None
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8,040 Posts

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Beneteau F310 ~ APOTHIC
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167 Posts
Discussion Starter · #4 ·

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Beneteau F310 ~ APOTHIC
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167 Posts
Discussion Starter · #5 ·
Just did some further research, and according to the Yanmar parts catalog, the oil pressure and engine temp senders are both switches, so they will not drive a gauge. This means I need to replace them with senders that will work on guages like Faria or Teleflex... Need to figure out how to find the correct after-market senders (I'm assuming the gauges are easy once I find the right senders...
 

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Just did some further research, and according to the Yanmar parts catalog, the oil pressure and engine temp senders are both switches, so they will not drive a gauge. This means I need to replace them with senders that will work on guages like Faria or Teleflex... Need to figure out how to find the correct after-market senders (I'm assuming the gauges are easy once I find the right senders...
So your research confirmed what I told you in my above post! Feel better?

You still want alarms, so don't replace the switches with senders (sensors). Either add senders or replace the switches with combination switches/senders. Again, what I said in my first post. If you check any marine retailer that sells the gauges, you will find the senders along with them. And most are standard, so you can usually mix and match brands.
 

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Beneteau F310 ~ APOTHIC
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167 Posts
Discussion Starter · #7 ·
So your research confirmed what I told you in my above post! Feel better?

You still want alarms, so don't replace the switches with senders (sensors). Either add senders or replace the switches with combination switches/senders. Again, what I said in my first post. If you check any marine retailer that sells the gauges, you will find the senders along with them. And most are standard, so you can usually mix and match brands.

Yes - I do feel better! You put me on the right track, but I still had to check it out. The thing that's making me nervous now is that I read a post somewhere indicating something about metric threads on a Yanmar block, so I'm trying to figure out whether I can buy one of the standard sensors with 1/8 size fitting, or if I need a special one, or some kind of an adapter.
 

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Yes - I do feel better! You put me on the right track, but I still had to check it out. The thing that's making me nervous now is that I read a post somewhere indicating something about metric threads on a Yanmar block, so I'm trying to figure out whether I can buy one of the standard sensors with 1/8 size fitting, or if I need a special one, or some kind of an adapter.
Good point about metric threads. Note that you can add a water temperature sensor many places in the water circuit with a tee. Just needs to be grounded to the block to complete the circuit. The oil pressure is tougher as you need to use that location. Not nearly as useful as the water temp however, so not a great loss if you decide its not worth it. Volts and fuel level are also more important than an oil pressure gauge.
 

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One of None
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Thing is.. even "marine" sending units are pretty cheap.. for temp, oil, water, volts.
 

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23 Posts
I to want oil pressure water temp gauges. VDO makes
Metric pipe sending units but I have not removed my
fittings to try to match up the Yanmar threads.
Looking on in intreats.
 

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One of None
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8,040 Posts
I've never even seen metric pipe anywhere in my trade HVAC, not that I ever thought of looking for it., my dad was a plumber too. so the MM is the size but not actually differen't from what is used here in the USA? seems so.

Diameter Nominal
DN
(mm) Nominal Pipe Size
NPS
(inches)
6 1/8
8 1/4
10 3/8
15 1/2
20 3/4
25 1
32 1 1/4
40 1 1/2
50 2
65 2 1/2
80 3
 

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I've never even seen metric pipe anywhere in my trade HVAC, not that I ever thought of looking for it., my dad was a plumber too. so the MM is the size but not actually differen't from what is used here in the USA? seems so.

Diameter Nominal
DN
(mm) Nominal Pipe Size
NPS
(inches)
6 1/8
8 1/4
10 3/8
15 1/2
20 3/4
25 1
32 1 1/4
40 1 1/2
50 2
65 2 1/2
80 3
Metric pipe sizes are very close, but threads are different. Slightly different number of threads per inch for the same OD pipe, and threads have a slightly different shape. See ISO 7-1. From the Engineering Toolbox online:

"NPT threads may look similar to ISO 7/1 threads. However, ISO and NPT threads should not be mixed. ISO threads have 55o taper angle versus 60o for NPT. The NPT root and crest configurations are also different from ISO. For ISO threads pitch is usually measured in millimeters (may be expressed in Inch). The pitch are different."
 

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Member
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23 Posts
Ok found out VDO makes a metric thread universal kit
With different size adapters for oil pressure and water
temp. That is what I am going to purchase.
 

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204 Posts
The sending units from later model Yanmars will fit the YSM. It is a common upgrade. Check with Mack Boring or Torrensen or Hoye Tractor.
I've seen kits from Hoye Tractor parts. http://www.hoyetractor.com/PROD/TS-1470.htm for the gauge sender, $15.75. They also sell an adapter so you can use the sender from the gauge kit for about $10.00.
The alternator from later GM Yanmars has a tach terminal, and is a straight bolt in, same size case etc. Look for Hitachi LR155, 55 amp. You may need to change out the fans, as the YSM is "reverse" rotation. The YSM had a LR 135, 35 amp. The 155 will use a 1/2 horsepower more than the 35 amp, when it is putting out its full 55 amps, which is not that often. You can find the LR155 on line for about $100.00. For some reason it is a few dollars cheaper than the LR 135.
I have a YSM 12 which is why I did the research.
Lou
 

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Jerry-Bayfield-Wisconsin
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1 Posts
I have a Yanmar YSB-8 engine on my 1977 CS27, which thankfully runs like a top. The engine panel, however, is in rough shape and due for a make-over.

As I understand it, the engine system has sensors for oil pressure, engine temperature, and voltage (off alternator). I'm wondering if the existing sensors can feed an analog gauge rather than the dummy lights they are currently connected to. If not, is there a moderately painless way to get this information in the right format? I am most interested in looking to have a temperature gauge and oil pressure gauge.

I also want to add a analog tachometer, but I believe that I have to have my alternator modified for a pickup before I can do this. (I don't like the look of the tiny-tach, which I think is my only alternative).

Would appreciate any guidance, as I don't have much information on how these work.

Thanks in advance,
Chris
I am about to create a new engine control panel for my boat's Yanmar YSB-8. I have purchased some inexpensive analog gauges (with sending units) from Amazon.com. (They're only about $15 each--they may be too cheaply made--we will see.) I plan to parallel the existing binary (on/off) sending unit output to the warning lights with the new analog gauge sending units so that I can SEE the pressure and temperature and also have a warning light/buzzer. I think the pipe fittings are 1/8th inch NPT. I can let you know how it all worked out next spring when I launch the boat in Lake Superior. Stay in touch. By the way, instead of a tach connected to the alternator, I ordered a hand-held tach that responds to a reflective patch on the engine pulley. (Normally, I don't need to know the exact RPM after I adjust the full-throttle and idle speeds.) The tach only costs about $20 on Amazon.com.
 

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A long time ago I fitted an oil pressure guage and oil pressure alarm to my old Volvo MD17C.
I put a wee T-piece in to the oil pressure port on the motor and fitted an oil pressure guage on to the bulkhead of the engine room (my engine room is open on one side so I can see the guage).
To the other side of the T-piece, I fitted the oil pressure switch again, and used it to close a relay (taken from a scrap BMW) that in turn called in a standard automobile horn (taken from another scrap automobile).
I put the horn on an engine room enable/disable switch so I don't get deafened if my head is in there during maintenance with motor stopped and ignition on. The horn is bolted to another engine room wall. It is very loud so anyone can hear it, anywhere on the boat. You need the relay as the oil pressure switch cannot carry the current for the horn.... the switch calls the horn in, but does not carry the current for the horn.
Remember to fuse the circuit for both horn and relay. The only melt-down I ever had on board was the one circuit I did not fuse on the boat.... the oil pressure switch.... and the battery just fried the cable in seconds.
With that lesson learned, it is still working, 20 years on.
The lot cost me about $30 for the (new) guage (0 to 60 psi), and about $10 for the other bits. When cold, my old motor at 2000 rpm will raise about 60 psi with new oil (15W/40 mineral), and new oil drops to about 35 psi when hot, and at the end of season to about 30 psi when hot.
.
 
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