Removing thermostat

[Steve B.]

This is a 93 350?

This isn't exactly the same:

http://www.mercruiserparts.com/Show_Pictures3.asp?dnbr=884720&ivar=images/COMMON/1719.png&inbr=8183&bnbr=160&bdesc=Thermostat+and+Housing

Looks like there is a sensor, and a sender.

mercruiserparts.com is a great resource, but I didn't find your exact one in there.

Steve B.

[DWhynot]

No, it's some sort of sensor. There is a wire connected to it( obviously not in the pic) along with another wire connected to the sensor in th first pic( apparently the temp sending unit). Does anyone know what the sensor is in the second pic i posted of my Tstat housing (starboard side)? You might be able to get a better idea of what is what by looking at the third pic...or link to pic. Thanks for the reply

Just a wag, but does it go to an overheat buzzer/alarm?

Edited December 13, 2011 by DWhynot

[martinarcher]

The sensor on the left side (starboard) is the temp gauge sender and should have a single brown wore attached to it (if I remember correctly). I'm surprised it is screwed into the t-stat housing as it is usually screwed into the hole in the intake manifold to the starboard side of the t-stat housing.

The other sensor I would guess is a temp switch to trip a overheat buzzer. The 80's bu's don't have those sort of luxury features.

[james11music]

Thanks for all the input guys. Hopefully i'll have some time before the weekend to investigate further. I just need to put the battery back in and then reinstall the impeller and housing. From there i'll try grounding out both wires to see what each do. I'll keep you all updated and hopefully i'll have my temp gauge working soon.

[james11music]

Now that i have some time off, i finally got around to firing up the boat and to my suprise, the temp gauge works! Not sure why it decided to start working, but i'll take it. Before i could fire it up i had to put the impeller housing back on(old style, two piece) which took a little bit of work being as i hadn't done it before myself. It wasn't too bad, just a little tricky getting all of the gaskets and plates to line up. After that i started it up and was pleased to see water flowing out the exhaust after about 10 or 15 seconds. I hopped back into the boat to check for leaks in the impeller housing, there were none. Then i checked the tstat housing and water was coming out the back in a couple different streams. So i shut her down and took the tstat housing back off. What happened was that i didn't clean all of the old gasket off of the engine block. The gasket had pretty much become one with the block so after 15 minutes of scraping i was ready for take 2. I started it up and no leaking. After that was taken care of i took both wires that go to the tstat housing and grounded them to the block to see which did what. MartinArcher was right about the temp sending unit being the sensor on the starboard side. When i grounded that wire to the engine it pegged the temp gauge just like Ruffdog said it would. So now i'm thinking all i need is a temp sending unit, easy fix. I decided to hook the wire up to the sending unit just for kicks, but didn't expect anything because the temp gauge along with a few others havn't worked since i've owned the boat(3 years). It all of a sudden works and holding steady at about 135ish degrees! And as if that wasn't good enough, my oil pressure gauge and battery voltage gauge decided to start working also! I'm guessing there is a loose connection behind the dash, but it is such a mess of wiring back there i really don't wan't to look unless i have to. Anyways, just wanted to give an update with my good news. Hope everyone had a merry christmas.

[martinarcher]

Awesome. Glad it's all working for you. Sounds like a bonus Christmas present to me. I hear you on dash wiring. It can get nasty in a hurry. Anytime you back there take a fist full of zip ties and try to "harness" things together and route wires into bundles and over time it really cleans things up.

Oh and Merry Christmas! Hope your's was a good one!

[Lance B. Johnson]

Good to hear man. We are glad to help.

[wakeboarder3780]

...

The other sensor I would guess is a temp switch to trip a overheat buzzer. The 80's bu's don't have those sort of luxury features.

You aren't kidding. I learned this one the hard way with my 89 sunsetter. Scared the crap right out of me. Totally thought there was a buzzer for overheating. No there wasn't! Glad to have one on my new bu :D

[barefootdiver2000]

Ruffdog,

My temp gauge isn't reading. I put a new t-stat in and that didn't fix the problem.

I pulled the wire off the sending unit and grounded it and it did peg out on the gauge. So does that mean the sending unit is bad or the gauge or something else?

You kind of contradict yourself on posts #14 and #20 so wasn't sure.