Over heat sensor question

[pinellas50]

I recently purchased a 1993 Starcraft which has a Mariner 115 on it. As best I can tell the motor is a 1996 model. When I purchased the boat, the oil level alarm was going off. The owner disclosed that he believed the sender in the tank was bad and needed to be replaced.

I'll add now that I am a pretty good weekend warrior mechanic when it comes to cars/trucks. But this is the first boat I have owned and the learning curve is rather steep at the moment. And I'm still learning boat terminology so please bear with me.

Once I got the boat home I started to investigate. I tested the oil level sensor and sure enough it is bad. No problem, I already have a new resivor and switch ordered. However, while I was in there I was giving everything else a look see and I began tracing the wire coming off of the over heat sensor. Well that wire has been disconnected and is zip tied to something else in there so it doesn't move around.

I began looking at the diagrams for the motor and I am seeing that this one wire goes to a terminal block. The problem is I'm not sure what that is and the manual I have doesn't really give me an idea what or where this is. I began to assume that the terminal block is the black strip that a lot of different wires all go to..........and one of the battery power wires I think. But the last thing I want to do is assume here.

So my question really is only where exactly does this wire hook up? A, what I assume to be hot wire, going to a sensor that appears to be touching the motor doesn't make all that much sense to me. But I may be assuming here. If I can get this wire hooked up to the correct location then I should be able to do any diagnosis needed from the manual.

 

[pinellas50]

Re: Over heat sensor question

Disregard just about everything I just wrote. That's what I get for starting a post 24 hours after I have looked at what it is I am trying to talk about. I see exactly where this is supposed to go.

But the wire coming off of this sensor is not the color specified in the wiring diagrams and it has a male connector on the end of it that cannot go to the terminal. The wiring diagram says the wire for this sensor is black but the one I am looking at is white.

I noticed that there is one extra wire hooked up to the terminal already that is not in my diagrams. The sensor wire goes to this terminal along with a tan/blue wire that goes to the engine harness. A solid tan wire, that goes to the alarm module, joins these others at the same terminal block. But there is an extra tan/blue wire hooked up to this same terminal and this wire runs up to the top of the motor, to the rear of the motor, and then goes through a hole at the back of the motor, where theh spark plugs are, and disappears into the power head. This hole is right next to the heat sensor I am talking about.

And the next question I have is am I possibly confusing the over heat sensor with what ever this thing is I am looking at. The golden question here is does the heat sensor actually go into anything or is it simply held on a bracket and the end touches the metal of the power head near where the spark plugs are?

 

[Keybear]

Re: Over heat sensor question

Just wanted to say Hi from a fellow Pinellas Iboater. I am just going to pull my lower unit and rebuild my XR6 150 water pump, and stats. The guys here will get to you with the answer soon but I found that you have to be very specific. Good luck.

 

[pinellas50]

Re: Over heat sensor question

Hey there. I am trying to be as specific as my knowledge will allow me to be. I'll find a way to get a picture posted of the sensor I am looking at if needed. I'd really like to have this system hooked up or confirm that it is hooked up properly now.

I also plan to do a complete service on this motor very soon as I don't know its exact service history. I only know that new plugs were recently put in. Water pump and stats will be addressed.

 

[pinellas50]

Re: Over heat sensor question

OK. Here is a pic of what I am talking about. Is this the over heat sensor?

Here is a side view. The sensor is actually the copper thing in the back ground and kind of out of focus. My camera decided to focus on the spark plug wire.

And this is a picture of that hole I was talking about that has the tan/blue wire running into it. The hole is to the left of the suspected heat sensor and directly underneath the stainless, phillips head screw. You can faintly see the wire in black sheathing, running into the hole.

Any help identifying these things would be appreciated.

 

[pinellas50]

Re: Over heat sensor question

I'm still looking for help identifying these parts. My manual is pretty vague on this point.

My next question is exactly how does this sensor work? When it heats up does it cause a ground which sets the alarm off? I have traced through the wiring diagrams and I think I see where this sensor is supposed to hook up to. But this looks very different than the automotive world I am used to.

It looks like it bolts down to a "terminal end" which looks like nothing more than a solid piece of metal on the engine block. This terminal end is on the starboard side of the motor, near the botom of the power head, and near the rear of the motor. The problem is that the connector on the wire going to what I think is the over heat sensor does not match up to what is needed to hook up to this terminal end. It has a spade end on it which doesn't make any sense given what I am seeing in the wiring diagrams.

I was wanting to test the alarm module before hooking this sensor up to make sure this function is working correctly. My manual doesn't have anything on how to do this. And I'm not going to purposely over heat the motor for curiousity sake of course.

If I am going to short something out messing around with this please tell me now and I'll track down my marine mechanic buddy. But I like to fix/learn things on my own and not impose whenever possible.

 

[Mr. Florida]

Re: Over heat sensor question

That does not look like a heat sensor to me. They usually go right into the block. That is either a ground lug or a single insulated terminal point.

 

[Fl_Richard]

Re: Over heat sensor question

Where does the manual say the white wire connects?

 

[j_martin]

Re: Over heat sensor question

I don't think that's stock. The overtemp and oil alert alarm circuit is tan, or tan with a blue stripe. Compare that to the color of any other wires coming from the terminal block. With the key on, grounding the tan wire will sound the alarm.

I have no way of knowing what the device shown is.

hope it helps
John

 

[pinellas50]

Re: Over heat sensor question

I don't think that's stock. The overtemp and oil alert alarm circuit is tan, or tan with a blue stripe. Compare that to the color of any other wires coming from the terminal block. With the key on, grounding the tan wire will sound the alarm.

I have no way of knowing what the device shown is.

hope it helps
John

This helps a lot! Thank you! I'm guessing that the wire in the back ground going into the hole is probably going to the over heat sensor then. I double check the wire colors on that other wire(s).

The manual says that the over heat alarm goes to the terminal block I described above. But come to think of it, I'm not sure I paid attention to the wire color.

This motor came off a different boat(unknown what) so mabey the thing in the picture, what ever it is, had something to do with a guage or something on the other boat.

But you guys just nudged me in the right direction. Thank you!

 

[pinellas50]

Re: Over heat sensor question

I just wanted to say thanks again.

I was able to verify that the over heat sensor is the wire going through the hole in the back ground of my pics. It has a tan/blue wire on it just as you guys said. Everything is good to go with this aspect of the warning systems.

I still have no idea what that other thing is but it will remain unhooked and I'm not going to worry about it.

 

[pinellas50]

Re: Over heat sensor question

So I talked with the folks at the marine supply store today about this unknown sensor. They said it sounds like a sender for a temp guage or alarm. Obviously there had been something else in there on top of the factory alarm. The boat wasn't there for them to look at but they described this thing in the picture to a T. How it makes direct contact with the cylinder head.

This seems like an unusual way to measure the temp in the motor. Again I'm used to cars. I would think temp measurements would be much more accurate with a sender driectly in the water circulating through the motor.

My question now is are they right about this being a temp sender? If so, should I capatlize on the existing sender and find a guage that will work with it? Or later on put in a guage that has a sendor directly in the cooling system?

 

[Dukedog]

Re: Over heat sensor question

Yes they are. Thats a sensor for a heat guage. Water temp is better but that type is way more common on a boat. You might as well take it off even if you have a guage in your boat. The sensor and guage need to be compatible and probably no way of telling what kinda guage it was used with. Hope this helps...........D

 

[pinellas50]

Re: Over heat sensor question

OK. Thanks!