Three engine wires with no home?! H35.5

Jul 30, 2017
36
Hunter 35.5 Chicago
I have three wires that have lost their way.

One looks like a sender (second pic from the top). The "sender" appears to be brass, with a tiny pin sticking out. The sender has splines and appears it would be pressed into a hole.

Any ideas where these hook up or what they do?

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Last edited:
Jul 30, 2017
36
Hunter 35.5 Chicago
I’m hoping at least two are for an accessory I don’t have. I don’t have a saildrive.
 
May 18, 2017
8
Hunter 35 New Orleans
Engine compartment 1.JPG
Engine compartment 2.JPG
Here are pictures from my H35.5. Without a doubt the 2 connector plug is for the yanmar sail drive that you do not have.
I think your wire with the rubber hood containing the brass pin is the oil pressure switch. last wire I cannot tell you, but I do not have a loose wire like that on mine.
 
Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
I thought about those saildrive wires being used for something else. I'll look up and see where they go.
 
May 18, 2017
8
Hunter 35 New Orleans
The oil pressure switch wire goes to the engine control panel and will light up the low oil pressure warning light and make the buzzer sound. With that wire disconnected, the engine would run fine but you would not get any notification of an oil pressure problem. I would be concerned that the oil pressure switch has been significantly damaged with the brass part pulled out and it could leak oil. This switch is connected to a primary oil path in the engine and that switch is subjected to full oil pressure.

If you have not downloaded a copy of the 3GM30F Yanmar service manual with a wiring diagram, do an Internet search and do that. The wiring diagram may answer a lot of questions for you.
 
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HMT2

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Mar 20, 2014
899
Hunter 31 828 Shoreacres, TX
I had an oil preassure sensor on my Yanmar that went bad, I replaced it. It’s easy and not a very expensive part. Maybe that’s why the PO unplugged it?
 

HMT2

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Mar 20, 2014
899
Hunter 31 828 Shoreacres, TX
Currently, when you turn your key on and before you start it does the panel make a beeping sound and the oil preassure light turn on?
 
Jul 30, 2017
36
Hunter 35.5 Chicago
We get the beeping sound. Not sure about the light, but I don’t think so. I won’t get to check until late this week.
 
Feb 15, 2008
183
Hunter 49 Sydney
Hi, Just one comment may be of help. While my engine is not the same, there are two sets of wires there. One is Oil sensor's switch, ie it has or does not have oil presure (ie the oil light), the other is oil presure sender for the guage (ie PSI). On some yanmars they use the Oil sensor switch to enable field coils on the Alternator. It can be a tricky area. The last point to be care full with is the Oil Presure sender unit. Dont just assume its Yanmar. They actualy used 3 different types that are vastly different, but phislcay the same. The difference being which required due to different pannels and guages on the end. The sugestion above to get te Manual if you dont have is excelent idea, for long the long term as well.
 

AlexB

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Aug 9, 2016
37
C&C 36 Great Kills harbor.
Hi, if You look on the picture, where yellow wire with plug conected to oil pressure switch, below it corroded cylinder is oil pressure sender, which works with oil gauge. look for connector. good luck.
 
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Jul 30, 2017
36
Hunter 35.5 Chicago
The mystery gets thicker. In the first picture is where the rusty sender in AlexBs pic would be. The second pic shows where it would attach. You can’t see it well in the pic but the attachment point for the sender is plugged with an Allen headed plug.

Is it possible I never had a sender? Why would you remove and disable a $20 part?
 

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Feb 15, 2008
183
Hunter 49 Sydney
I can tell you why it might have been dissabled, I have contemplated also disabling mine though I would not do it that way. In the case of my engine (4JHTE). I have also have both oil switch, and oil presure sender , and another blank entrance into the oil chamber. My instruments are electronic, and all appear on the plotter, or my computer. So the sender units are different for this. On this engine with those sender units the senders are junk, and at best very tempremental. This first one of these failed scared the sh... out of me as I was probably 600nm from any land motoring wiht maybe 2 knts of wind, and the boat was maybe 12 months old. As soon as I saw the presure drop I turned off the motor and checked as much as I could. Oil presure was dropping down to about 2-4 PSI. Long story short it was lieing, presure was not dropping at all. Four senders later have added a mechanic old style one right at the engine, and pretty much ignore the electronic sender when it has its spassim. It works 99% of the time but that one percent gives my heart a run for its money especialy if Im working in or around coral reefs. They last about 2 years if ya lucky.It maybe in yur case the unit was damaged as someone tried to remove it also. I now carry a two new senders as a matter of course. I would just make sure that the oil switch... not so much oil presure sender, but the swithc one is working 100%. In my cases this is the one that will stop (shutdown) the engine if Im not paying attention to the oil presure. I have tested all my senders and sensorse, neverever let the shut downones not work, as for the oil presure much better to have it of course, but yea I can imagine the temptation to disable it.
 

AlexB

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Aug 9, 2016
37
C&C 36 Great Kills harbor.
it is not a misstery at all, i just copy your picture, my thought was, that it's your engine. so, if You do not have, sender, probably you do not have pressure gauge on panel. wiring usially universal, that is why it has unused plugs. sorry for my english, if you have ?????, do not hesitate to ask.