What Type of Engine Sensors for Aftermarket Guages?

[rardiH36]

Finally getting around to a "to-do" list item three years after purchasing my boat.

The PO did a very nice looking install of analog guages at the nav station for engine volt, oil pressure, and water temp. Wires were run into the engine compartment but were never hooked up to anything. I knew this when I bought the boat. Connecting up the volt guage was no problem of course, but as for the others, it appears that the PO abandoned the project before completing ... and never purchased the sensors.

I am not at the boat, so I can't post the actual manufacturer of the guages. Its an obscure brand anyway because a couple of years ago, I did bring the name home for an internet search. There were no hits; none.

Question is: Are temperature and oil pressure sensors more or less Generic? What should I purchase? Are the guages likely to need calibration?

I know that I will need T-fittings to add guage sensors without removing the existing water temp and oil pressure switches that trigger the engine alarm and warning light circuits.

Thanks for some education on this topic.

rardi

 

[tommays]

There are a few OHM ranges used in guages the brand used should allow you to find out the info


33 to 240 is common but not 100%

If you use the wrong sender it will work but give bad info

You can check each guage by touching the (if wired correctly) wire to the block which should peg the guage

 

[Bill Roosa]

Most gages for temp and oil pressure...

are just resistance meters.
SO
You could trundle off to Radio shack and buy a variable resistor (0 to 100 ohms should work fine) and test the unit to see what resistance is actually needed for full deflection of the gage. The variable resistor just replaces the sending unit. Once you find the setting that gives 0 and full deflection just take your OHM meter and measure it for both.
If you only have a single wire connection the other wire would go to ground on the engine or battery negative.
Then go to DigiKey and find the sending unit with the right specs

 

[Stu Jackson]

Teleflex

 

[Old Skool Neil]

The PO did a very nice looking install of analog guages at the nav station for engine volt, oil pressure, and water temp.

This raises a question: are the newly installed gauges at the nav station a duplicate set to those at the helm station? If so, I think (not certain) you might need special senders.

I worked at Jensen Marine in the 70's and one of the product lines we built were the DeFever Trawlers. They had two steering stations, one in the main cabin and the other on the flybridge with a full set of engine gauges at each. We had to replace the oil pressure and water temp senders supplied with the engines with "dual station" senders. I'm thinking you might need the same.

 

[RAD]

Or just abandoned the present gauges and buy new....there not that expensive and will come with sending units
another thought is post a picture and maybe some one will know what you have

 

[rardiH36]

Thanks all. The suggestions helped:

-- The engine's instrument panel in the cockpit doesn't have gauges for temp and oil pressure. Just the audible warning and idiot lights. I won't be modifying this system. The existing Yanmar hi-temp and oil pressure warning activation switches will remain in place. I'm looking to finish the nav station gauge thing mainly because the gauges are already in place. Plus installing sensors for the gauges will give me some added information about the engine's condition when running. And if the warning alarm sounds at the engine panel, I'll have added confirmation that I really do have a problem, or conversely its a false alarm and I'm probably safe to keep running the engine until the alarm circuit can be checked. I know that T-fittings are needed so both the original switches + the gauge sensors can share the same engine fitting. I have read, however, that this can compromise the temp readings.

- I took a look in my miscellaneous electronic parts box. Several potentiometers, but all 5k ohm or more. Just a smidgen of a turn changes the resistance from zero to well over 100 ohms. So yes, it’s off to Radio Shack.

- Yes, appreciate the idea to instead buy a new gauge plus sender kits. If I get back to the boat over the next several days, I'll take a picture. But since an internet search under the manufacturer's name yielded no results, chances are we will all be scratching our heads.

Again thanks.

 

[rardiH36]

A Picture, More Info and Another Question

Several weeks ago we threaded about an after-market sender for my "Airguide" brand temperature gauge. Here's more background and another question. Some participants asked for a picture:



It's a pretty thing. Subsequently I searched further on the internet. Apparently Airguide gages were a well-know brand way back when. Mine must be a retro knock-off. I was not able to find any info about modern day manufacture or the specs for the sender.

Per Bill Roosa's suggestion, I haven't yet done the variable resistor measurement to identify the correct ohm range for the eventual sender. But I will.

Here is the other question. My engine only has one location on the engine block for a temp sensing device. It is currently occupied by the engine hi-temp alarm switch. I want to leave it there because the audible/visual alarm is important to preserve unaltered. So where to install the temp sender for the gauge? I'm thinking as follows and would like comments. My engine has an external heat exchanger that is mounted on a bulkhead a couple of feet from the engine. Anti-Freeze circuit water from the thermostat area is routed to the exchanger via standard coolant grade hose. I am thinking to place an in-line T-fitting in this hose very close to the engine. Two hose clamps on each side of the fitting. The gauge sender would be mounted in the "T". I would need to somehow secure a negative 12V wire between the sender body to the engine block (or other ground point). The plus side of the sender goes to the gauge. I recognize that the temp reading at this location will probably somewhat lower than otherwise. But it is relative info that I am after. I will be able to observe and record the base-line. Then if the engine temp alarm goes off at some point, I can then look at the gauge to verify that temp display is higher than normal and know that the engine is in fact running hot.

Thanks in advance for warnings and alternative ideas.