Water or Engine Temp

[bfraser4070]

Hello:

I am repowering a WA going from OMC/Johnson 225 to Mercury.

I have a guage that just says TEMP(See attached Photo).

Excuse my ignorance, but does this guage measure Water or Engine temp?

If water I know I can hook it up to the tan wire on the control harness.

If engine temp can this be hooked up to the 225 EFI(3.0L)?

Thanks in advance for your help.

 

[Dukedog]

Re: Water or Engine Temp

Could be either but..........Your probably gonna need ta get a different guage that's compatible with your Merc temp sensor. Not a slomc guy Don't know for sure but I wouldn't take tha chance. Get yourself a water pressure guage if ya don't have one. Way more useful tha temp. Tha Merc wireing harness should have a motor temp warning buzzer thats usually more accurate tha most temp guages. Its still a good guage ta have though once you have an idea as ta where tha NORMAL temp reading is supposed ta be............D

 

[bfraser4070]

Re: Water or Engine Temp

Thanks Dukedog for your response.

I believe I already have a pressure guage.(see new attched photo).

It has a black tube running to the engine which according to the service manual I can connect to the grey tube on the back of the engine?

I am selling the boat once finished since I bought a larger one.

Just want to make sure everything is working properly for the new owner.

Any suggestions would be appreciated!

Thanks in advance

 

[Dukedog]

Re: Water or Engine Temp

Guess you could tie it into tha tan and see what happens. Don't think it will hurt anything. Like I said, not a OMC guy. Don't know their configuration on temp sender. It may have an actual WATER temp sender. Maybe some one that knows for sure will jump in here. Anytime we change motor brands on a boat, we change everything just ta COA's Sometimes savin' a dime cost ya a dollar..................D

 

[Texasmark]

Re: Water or Engine Temp

The tan wire goes to the over temp switch which should be nothing more that a switch which closes at roughly 190F and in doing so grounds the tan wire. I have been through that circuit on my Merc several times. If it shorts out due to overtemp it sounds the overtemp horn in a constant blast, not intermittent beep.

This looks like an analog gauge meaning that you need a varying resistance or pressure to control it meaning that if it is temp you need a sending unit mounted in the cooling water jacket somewhere. Heat would change the value of resistance if an electrical circuit, hence deflection, or heat would expand the fluid in a fluid system causing deflection. The electrical system would be via wire, the fluid via a tube.

Otherwise it is a pressure gauge (i'd assume) which is operated by a tube that connects back to the engines water jacket.....you ought to be able to look on the rear of it (the gauge) to see if it has wires or wires (lights) and a tube. If it has a tube, you will need a fitting on the Merc to accept the tube. l know they exist as we were talking about that subject on here yesterday.

You may luck out and be able to use it (the existing gauge) as the water pressure of both engines is probably about the same and probably around 10-15 psig at max rpm......that's what my Merc manual says for my engine.

My 2c I am guessing at half of it, but I think it is an educated guess or I wouldn't be wasting your time.

Mark

 

[Dukedog]

Re: Water or Engine Temp

Does tha tan wire have a "bullet" connector or an "eyelett" type connector?