water temperature sending unit.

[Calabrio]

This nightmare of a boat I recently purchased has a teleflex water temperature gauge in the dash. When it was hooked up to a Mercury sending unit the needle spiked, rendering it worthless.<br /><br />I purchased a teleflex sending unit, and I can not figure out how to hook it up. Specifically, where it'll fit in the engine. The clymer manual doesn't address this issue, and the holes I see on the engine appear too small, or aren't threaded.<br /><br />The engine is likely to be a pre-89, 150hp Mercury Outboard. Can anyone tell me how to connect an aftermarket sending unit up to it? And, is 3/8'' the right size?<br /><br />Any help would be appreciated.

 

[KCLOST]

Re: water temperature sending unit.

Calabrio,<br /><br />I'm not sure about the size of the unit.... But I can tell you that the unit for your engine will not be measuring water temperature, it will measure the head temp below the #2 cylinder (left side)..<br />That is where the sender will go. Cylinder head water jacket has a hole in it to allow the sender to go through into the head. Your overheat sender is at the same place under the #1 cylinder (other side bank). You will probably get readings of 180-200F at WOT... You should have a sender with a 15-1/2" lead...

 

[Calabrio]

Re: water temperature sending unit.

Thanks for the response,<br />I know the spot you are talking about, and currently there is a mercury bracket, with three holes, over it.<br /><br />The teleflex sending unit appears to not need that hardware.<br /><br />The hole under the #1 cylinder is faily shallow and doesn't seem to be threaded. Does this sound right?<br /><br />EDIT: I just went outside with the 3/8" Teleflex sending unit. I removed the Mercury bracket exposing the hole, which also appears to have a diameter of 3/8. As mentioned, it's a fairly shallow hole, with a metal bottom. There doesn't appear to be any threading in the hole?<br /><br />Does Teleflex make an appropriate sending unit for the mercury outboard?

 

[KCLOST]

Re: water temperature sending unit.

I'm sorry Calabrio, I was incorrect before I edited my post. The sender goes under the #2 cylinder (left side of engine). THe overheat goes under the #1 (right side). (maybe it doesn't matter)<br /><br />The hole under the number 1 cylinder is for the overheat normally... The bracket is what holds both types of senders in place on either side. A nut on my threaded temp sender tightens down on the bracket to secure the wire. But I don't believe the hole itself is threaded. The sender much touch the metal at the bottom of the hole, if you can get the sender in that hole you sould be allright. It's worth a shot to find out anyway.

 

[Calabrio]

Re: water temperature sending unit.

o.k.<br />With that said....<br /><br />On the starboard side of the engine, the location under the top cylinder is full. There's a wire running into it, a rubber cover, a spring, and then it goes into some kind of sensor that is mounted inside the hole. I'm assuming that is the alarm.<br /><br />On the Port side, there is a 3/8'' wide hole. It is not threaded though. Covering the hold is a piece of hardware with 3 holes. 2 holes for bolts to mount the plate, and the middle hole to install the mercury sensor.<br /><br />I was only able to find 3/8 and 1/2'' teleflex sending units. If there was a small, narrow, mercury sized one, I think my problem would be solved. <br /><br />Is there something I'm doing wrong? What else do I need to do? Why is it, that even though most new cars are infinitely more complicated then these old outboards, they seem so much easier to work on? Why is information regarding boats so difficult to obtain? It's like secret. Why is it so difficult to locate a model year on an engine, or the factory output? <br /><br />Anyway, I guess I've found the right location now. But, how do I install it? If the hole is 3/8'' in diameter, I guess the 3/8 sending unit isn't going to work?

 

[KCLOST]

Re: water temperature sending unit.

Check this site out with a diagram. Does the bracket with the three holes have a threaded hole in it for the sender? I will look at mine tonight and see what I find...<br /><br />The Part# for the proper sender is 12415, if you were to order it through a Merc parts dealer...<br /><br /> http://www.dougrussell.com/partscat...2415&BlockNumberList=22,100,90,290,360,25,100 ,10,370,10,18,11,13,20

 

[Calabrio]

Re: water temperature sending unit.

A mechanic said he hooked up the proper Mercury sending unit and the gauge spiked, burying the needle to the right. The assumption was this was due to incompatible sending units.<br /><br />Does anyone know if a Mercury sending unit will work with a Teleflex gauge?

 

[gss036]

Re: water temperature sending unit.

Are you sure you had to old guage wired properly? If you got the alarm/guage backwards, the temperature guage will peg out and niether will work for you. Worth a check. I say this because on my merc 200 both wires are tan, one has a light blue line on it, the other is solid color.I had a wring harness problem and even the mechanic got them mixed up, switched them around they worked great.

 

[KCLOST]

Re: water temperature sending unit.

If your telflex sender will not thread into the bracket hole you're probably screwed....(pardon the pun)<br /><br />I would recommend gettin the sender and gauge that is listed on the web link I gave you earlier... <br /><br />Does the bracket have threads in it where the sender goes through?

 

[Calabrio]

Re: water temperature sending unit.

Problem number one-<br />the expert at West Marine provided me with a the sending unit for a Mercruiser, not a Mercury outboard.<br /><br />I went the Mercury dealer and installed the correct part (as described above) and it appears to be working well. <br /><br />Thanks everyone for responding. <br />These boats are tricky.