Water Temp Gauge

[henryb]

I finally got the new Mercury outboard compatible Water Temp gauge from Crowley. It is a 60-200F range gauge, as I have read our engines run cool around 120F or so.

The installation went smooth, I followed the wiring instructions carefully, it lights up, but it doesn't seem to read the temp from the pre-wired tan wire in the helm? Not exactly sure how to test it, if the temp sender is working or not? What voltages should I be getting from that wire to ground?


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[Dr Honda]

Did you make sure it's hooked up at the engine?

 

[Dr Honda]

I guess I should have read it better.


You won't see any voltage from the sender. It changes resistance with temp. SO... set your meter to Ohm's, and make sure the sender body has a good ground. (If the threads in the engine have paint, it won't ground well)

 

[henryb]

Got it... Checking that now... The actual tan wire connector at the sender in the engine was not in pushed in really tight? So maybe there is hope!


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[henryb]

Also found that the bolt holding the sender itself was loose. I tightened that and re-seated the tan wire connector a few times. But still no reading! :-( taking some Ohm readings now.


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[henryb]

Ok, so I am getting some resistance numbers, and they are getting up to the tan wire in the helm. I'm just not sure if they are good enough or correct?

I was getting on my meter about 0.0049uF ... Not sure if that makes sense or not?


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[Dr Honda]

you are reading capacitance if you are getting "Micro Farads".

As far as the actual numbers... you will need that info from the gauge manufacture.


One quick test I would do.... Ground the tan wire at the engine, and then just check the tan wire at the helm. It should read close to 0 ohms. (almost no resistance) Basically.. make sure the wire between the engine and the gauge is OK.

 

[henryb]

Now that I have figured out this meter, it reads ohms and capacitance on the same setting? My dads Fluke meter does a million functions, (it has a 100 page owners manual). So yes there is continuity on the tan wire and it is reading about 20 ohms... But the engine is cooled off now.


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[henryb]

I took the boat out for a 15 minute run at 40mph. Gauge still not reading. Checked the resistance and it was reading 54 Ohms right to the back of the gauge?

This is a Mercury brand gauge, apparently compatible with all Merc outboards according to the instruction manual?


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[Dr Honda]

Well.....


Then you need to make sure the gauge is OK. On the sender line from the gauge... Open SHOULD read low... and ground should read high.


So, ground the sender wire right at the gauge, and see if it goes to full temp.

If that makes the gauge move... then the sender is bad.

As far as "Compatibility"... as long as you used the sender from the gauge... you can put that on a go-kart. (assuming you have 12v)

 

[henryb]

Yep, the gauge us working fine! I touched the sender post and the ground post (with the ignition key on) and the gauge went right to Hot.

So I guess I need a new Sender!

Thanks for your help!


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[henryb]

FYI, the sender unit is probably the one that originally came with the boat? The gauge did not come with a sender.


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[henryb]

I think I will take this opportunity to replace both starboard and port side temperature sensors. Especially after reading the "sticky" post on "best performance improvement"... Basically changing the other temp sensor will help the engine perform better, easier starts, better top end.


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[Dr Honda]

FYI, the sender unit is probably the one that originally came with the boat? The gauge did not come with a sender.


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Then it may never work.

I would get a sender from the gauge manufacture.

 

[henryb]

The gauge is made by Mercury Marine? Not sure where to go to get one? Maybe I will call Crowley and see what they say?


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[henryb]

Talked to one of the technicians at Crowley.... and they suggested to replace the senders with the Mercury OEM sensors. So I put both on order at a local shop, hopefully they will be in by the weekend. Will update when they arrive.

 

[henryb]

Interesting finding today (Canada Day)... That I was checking out the other temp sensor (port side)... The one that the engine / cpu uses for controlling starts and oil mixture and timing advance and so on... Well it's missing!!! And there is no retainer clip or bolt either!

I'm surprised the engine runs at all???

So my question is which connectors is that sensor supposed to be connected to? And where are they? The Mercury Service manual says there is 3 wires Tan/Blk, Tan, Blk... But you would think they would be all together? But I don't see them?

Regarding the Bolt, I think I should be able to remove the starboard side sensor and find a SS bolt to match at the hardware store? But the retaining clip will need to be made? That will be my mission for today!


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[Dr Honda]

On the 210 engine... you have carbs. SO... the Port side sender isn't used the same as the 240. (dang near cripples the 240 when it's bad)


Let me dig into that one for you. I think it still controls the timing.

 

[Dr Honda]

Welllllllllllllllll..................................



Now that I looked over the 210 wiring diagram... I know why your temp gauge doesn't work. It takes it's reading from the port side temp sender. SO... if it's missing... that's why there's no reading.


There should be a black (ground), 2 tan/black, and Tan/Blue wires, the sender hooks to.

 

[henryb]

Ok, here's the deal... The starboard side sensor is there, it's the one with a spring and one wire (tan/blue)... It is connected to the tan wire... which is supposed to go to the gauge. Again that does not match the schematic!

I found the 3 wires that are supposed to be connected to the port sensor: tan/blk; blk; tan. However, I can not find the wire that the starboard sensor is supposed to be connected to: tan/blue.

So I'm a bit confused on what I should do once I get the new sensors? Or is that tan/blue wire hidden somewhere?


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[Dr Honda]

If it doesn't match the schematic... then you probably should look things over. BUT... the output of that sender probably doesn't match the other sender.


By Merc's diagram... the single wire sender goes to the control box... and the multi wire sender feeds the gauge and another line on the control box.

 

[henryb]

Yes, agreed... I just can't find that one connector that the single wire sensor is supposed to connect to... Tan/blue. Any idea where it is supposed to be?


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[Dr Honda]

I'd start at the control box, and work backwards. You may find it was cut/patched somewhere.

 

[henryb]

Ok, I found the tan/blue wire coming from the control panel (ECM) and followed it... It goes down the black cable that has the remote tach connectors and eventually just goes up to the helm? Although I couldn't see any tan/blue wire up in the helm either?


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[henryb]

You would think that the port side sensor (the one with a spring and a single wire) only has a cable length of about 4 inches... That the connector would have to be right in the vicinity of where it mounts?

Also another peculiar thing... Because the port side had no sensor, bolt or retainer, I wanted to make sure I could match the bolt size and thread... So I tried to thread the bolt from the starboard side. But totally to my surprise, the threads are different? Took a picture and there is no broken bolt in there? I'm wondering if there was ever a sensor on that side... No wire, no bolt, no clip... the surface is painted as if there has never been anything in there??? Just a thought?


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