Temp gauge sender

[JimOHoffmann]

I have a 1988 Mariner 60 hp on an 88 Tracker Tx17. It has a water pressure gauge, and I want to add a water temp gauge. I bought the sender from my Mercury dealer. But the only place I see to put the sender is the hole that has the fitting for the pressure gauge hose. This is on the rear of the powerhead, below and to the left of #1 spark plug. I thought of using a tee and hooking up both senders, but there's not a lot of space. And I don't know if the temp sender will be accurate if it's not screwed into the head.<br /> Any ideas? Thanks, Jim

 

[muskrat]

Re: Temp gauge sender

leave pressure gauge for maintance for your water pump pressure.motor has a overheat alarm built in.

 

[JimOHoffmann]

Re: Temp gauge sender

Alarm sounds after wot run for 15 - 20 mins. <br />Water pump relaced by dealer. He also ran boat on river and checked with heat gun. I would like to see what the temp is when the alarm sounds.<br /> Thanks, Jim

 

[schaiss]

Re: Temp gauge sender

Those temp alarm switches are designed to trigger at 240 degrees +/- 5 degrees. The switch should be located in the head and have a single tan wire coming out. When the temp of the sensor reaches 240 the metal inside it grounds out to the metal in the head, triggering the alarm. The alarm you are getting may not be from the temp unit. These switches actually monitor the temp of the metal on the head, NOT the water! Temp gages on outboards are not usually installed at the factory because THEY are considered to be unreliable. You can test the temp sender by pulling it out of the head, put ignition switch to "ON" (DO NOT TURN ENGINE OVER), heat the bottom of the switch with a cigarette lighter, (NO TORCHES), when the base of the sender hits 240 (use a thermometer for cooking a roast in the oven)touch the base of the sender to a good ground point on the engine. ALARM!

 

[JimOHoffmann]

Re: Temp gauge sender

Thanks for the info, I'll try that.<br />JIm

 

[Hooty]

Re: Temp gauge sender

240*! For an outboard? Where'd that come from?<br /><br />c/6<br />Hooty

 

[KCLOST]

Re: Temp gauge sender

Hooty, It comes from metal temp measurements around the head, which is just near the combustion chamber where temps reach crazy numbers...<br />Mercury did this on black max motors in the eighties....<br />I agree with Aquasportser on this one for that reason.<br /><br />The best way to check this is to remove the overheat sensor and see if it is actually touching metal and not entering the water jacket... I would bet that it never enters any water and is fixed to metal....That explains the 240F number, however water temps may be somewhat lower at the same time the 240F sensor goes off... The same system is on my 1986 175hp V6.<br /><br />Boat4fun, if you do install a temp sensor, I would recommend that it measures thr same.... Just so you can compare apples to apples, so to speak.... However finding another place to install it is a problem on a single head engine.

 

[Hooty]

Re: Temp gauge sender

Hummmm. Okay but 240*? I have a '87 2.4 and the alarm switch and the temp gauge sending unit are in the same place, one in the port head, the other in the stbd. The temp gauge never goes over 170*. I don't trust the temp gauge but just for grins, I checked the head temp at the sending unit with an infrared thermometer and they were surprisingly close, but again, nothing approaching 240*.<br /><br />c/6<br />Hooty

 

[schaiss]

Re: Temp gauge sender

240 is the hi limit set by Merc. If the metal temp of the head hits that point and triggers the alarm, it's time to slow the engine down and look for trouble. If the engine is equipped with a properly functioning lube alert module, this over temp condition should cause the engine to drop down in speed, to save the engine from burning itself up! FYI The thermostats in those V-6 engines should open up at about 140 degrees (cooling water temp).

 

[KCLOST]

Re: Temp gauge sender

Hooty,<br /><br />That sounds like the same system I have.... I would hope that you didn't measure anything close to 240F or you would be in trouble. <br /><br />The overheat alarm is the only thing we need to worry about concerning the 240F number... It can easily be determined if that's the max reading to set it off, by removing it and seeing what it is measuring, (metal or water)....<br /><br />My temp sensor also measure metal. It never enters the water jacket, it passes through an opening in the water jacket cover and sits on the top of the cylinder head.<br />This is confirmed by the fact that there is an opening in the cylinder cover water jacket gasket that seals water from getting to the overheat and temp sensors. I have an old gasket on hand that I checked...<br /><br />Your engine may be different however, I'd like to know what you find, if you feel like doing some checking....