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1996 Mercury 50hp 4 stroke

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grw1cop

New member
I’m adding oil, temp, and trim gauges. Appears the boat may have had two unknown gauges in the past. As in most older boats (this one is a Godfrey pontoon) wires have been cut, removed, or added with no rhyme or reason. I’m having problems identifying the engine wires going and coming from the sending units and where they actually go. The temp sensor (I think) has a grey/w black stripe and a black (ground) and what I think is the oil sending unit has a single tan w/ white stripe. They both go into another small harness to ???. My problem, where/what do I hook up to go to my console?
 
I can suggest two possible solutions. If you have an ohm meter you can put one connector at a known wire end (such as the oil pressure sender) and then go hunting through the wires available in the front to see which one has continunity and second just run a new wire and don't worry about the old wires.
 
Thanks, I thought of that but I really need to know where the wires which are already connected to the sending units go…ie; tan with white stripe (oil) and grey with black stripe… I don’t want to add any wires that aren’t needed…
 
Just as an afterthought, Mercury says the oil sender wire should be light blue and the water temp wire should be tan. There is no light blue wire (that I can find) and there is an empty tan wire going to the console along with the brown w/ white stripe which I plan on using with my trim sending unit.
 
Wow… I thought there were some Mercury gurus out there! I just finished putting in my trim sender unit and gauge, but I think I put an incompatible gauge in.…reads up when the motor is down…down when the motor is up….am I missing something or just ignorant? I even tried reversing the ignition and sender wires…nope, just pegs the gauge as soon as the key is turned on…
 
Well, guess what…the guy sold me the wrong gauge! I purchased a Faria Mercury trim gauge and a Mercury oem sending unit and it works perfect… now for the oil gauge… There is a oil sensor or sending unit above the oil filter. Like I said, it has a tan with white stripe wire…what would happen if I added another wire and hooked it up to a oil pressure gauge? I also think I can do a temp gauge (one of those that you pull a upper cylinder bolt and put the sensor there) and wire it to my gauge…anyone have any suggestions…?
 
There is no reason it won't work as long as you remember that the sensors provides a variable resistance, essentially a partial ground to the gauge. The gauge is still going to need a power source which is likely to be 12 volt (check the other gauges to be sure). Often the temp sender is put near the Tstat or close to the end of the cooling system to sample the hottest water, if you are removing a bolt to install the sender make sure that everything seals up right and go for it. Hope everything works out well for you.
 
Thanks, Swagonmaster… I’ve already got all my gauges and hots (ignition), grounds, illumination wires in. Replaced all of them with nice looking Faria Chesapeake. Everything is beginning to come together. If I add the other wire with the power from the console, will that cause an issue with what is already on the oil sender? It does have a bullet pigtail w/out any wire connected. That is also tan with the white stripe. I’d just have to run the added wire to the console. If I knew how to attach a photo here, I could show you.
 
If all of your gauges have power then the only thing left to do is hook up the wire from the oil sender to the sender side of the gauge.
 
As to pictures, if you go to the advanced icon at the bottom of the message box it will take you to a much more gadget filled message box that has under additional options the box to choose to add atachments.
 
Thanks, I tried all of that but not much of a techie… I use my iPad for all of my searches and such… pop up said I was performing an unauthorized action and had to close it and refresh the page…ugh.
 
Ok, I’ve got the trim and temp, added and also changed all the old gauges with new…they all work great! Tried the oil pressure hook up but that didn’t work. As soon as I hooked them up and added power, the alarm sounded and wouldn’t turn off even with the motor running. I’m about to give up on adding oil pressure gauge and just stick with the alarm…unless someone has any suggestions.
 
Use an ohmmeter to see if the oil sender changes resistance when the engine is started, I don’t know if you will see a variable reading or just on/off. You can also try lying to the gauge, disconnect the wire and see what it says then ground the sensor wire and see what you have.
If there is no change then you have a bad sensor or no oil pressure.
 
I’ve been running the boat a couple of times a week and have no issue with its operation…runs great at 16-18 mph, 5400-5500 wot. So I know I have oil pressure. Lol…. I’m wondering if the oil pressure sender is a pressure/no pressure switch. Is that such a thing? I believe that part is all oem and when I added the gauge to it, it just causes a dead short since it is also going to the alarm.
 
Yes there is such a thing , the alarm likely needs a switch that goes to ground at 8-10 psi to turn on a light or in your case an alarm, a real gauge needs a variable resistance sender to allow it to report changing pressure. I have seen folks install a tee to let them install both types of senders to allow both alarm and gauge to work. Since either sender should be at the end of the wire system for the gauge it shouldn't cause a short as in blow fuses but it could go to ground to turn on the alarm which would cause the gauge to peg the needle.
 
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