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Over heat alarm on 496 HO Merc

N

nabholz

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I have a 2001 baja outlaw 25&#

I have a 2001 baja outlaw 25' that has the over heat/low oil alarm going off on it. I had the impeller changed out and changed my sensors. By the gauge it is only getting up to 175F and looks to have plenty of water coming out of the exhaust. I unhooked my low oil resivoir thinking maybe it was the sensor...No change. It does it at different time also. Some times right after getting on plain then sometimes never. Any idea's???
 
"Well I cant see the serial Nu

"Well I cant see the serial Number on the engine cover, it has faded out. But the motor usually runs around 165F but if I hammer it and it goes up to 175F the alarm goes off. I talked to a bunch of baja guys and they said there's gets up to 190F without alarms going off. Would it hert to pull the wires off the temp sensor just to check it to see if thats what it is???"
 
well its either that SN or thi

well its either that SN or this one i found on the maintenance manual it is OMO25795 that sounds} more like it.
 
"Don't forget, the engine

"Don't forget, the engine OIL Pressure SWITCH is usally part of the inputs to the warning horn system, whether its controlled by the ECU or not.

If the warning horn is ECU controlled, there are two separate inputs (NO and NC) - you can isolate these at the inputs to the ECU to see which may be at fault.

Also, good idea to use an IR temp gun to verify the info the gauge supplies - their accuracy is much better than the gauge's."
 
Thanks i have a friend with a

Thanks i have a friend with a IR gun i will double check with that. Forgive my ignorants but what is "ECU" and "NO and NC" Thanks Makomark
 
ECU = Electronic or Engine Con

ECU = Electronic or Engine Control Unit

NO = Normally Open switch contacts

NC = Normally Closed switch contacts
 
Thanks for you help. One thin

Thanks for you help. One thing I do know i have plenty of water coming out the exaust when idling. Also the temp never gets over 175F at its hottest. But I will try the IR gun
 
"The stated gauge accuracy &#4

"The stated gauge accuracy (teleflex and faria) is +/- 15 deg, F. If you accept that as fact, your 175 reading could be 190. Use of a backup device is usually a good idea."
 
I changed out my Thermostat an

I changed out my Thermostat and thought I had fixed it. I dropped it in the water ran over to the island. (place where everyone goes) Never got over 165F. After a day at the beach. I left and got about a mile down the water and it got to about 190F alarm went off. So seems like it is something to do with temperature. I am going to take it in and have them flush the system out and see if that changes anything.
 
Is your engine FWC? Air in th

Is your engine FWC? Air in the cooling system will cause false temp. readings.
 
what would cause air in the sy

what would cause air in the system and how do I resolve it??? Could that be causing the speratic temp flux.
 
That's it; antifreeze in t

That's it; antifreeze in the engine w/a heat exchanger. Opening the cooling system downstream of the fill point can induce air. Loosen the fill cap and idle the engine so it can burp. Some cars have air bleed valves. Don't know if boat systems use them.
 
The antifreeze fill pressure c

The antifreeze fill pressure cap may not be working. Test it or replace w/the same model.
 
"If it has an overflow bottle,

"If it has an overflow bottle, does it have coolant in it? Is the hose still flexible or hard and brittle? Where is the bottle, height-wise, to the heat exchanger fill cap?"
 
Thanks guy I will look into th

Thanks guy I will look into the cap and see. Im starting to think Im going to have to bite the bullet and take it to the shop!! As for your comment Mako the overflow bottle is about level with the heat exchanger. I will also check the hoses and see if they are soft or hard. Needless to say Im running out of patients with it. Im just trying to save money and figure it out myself. Instead of paying for a shop to figure it out.
 
"If the cap's seals are le

"If the cap's seals are leaking or the hose connecting the bottle to the HX is cracked (leaks), then the HX will suck air in when the coolant contracts. As noted above, air in the system will result in hot spots. A pressure tester is required to check the cap.

I've found that purging all the air out of the HX on the first attempt is rarely successful. It usually takes a few hot/cold cycles to 'burp' the system. You can monitor this via the fluid level in the bottle."
 
So the cap needs to be snug?

So the cap needs to be snug? Im not sure if I snugged it or not. Can it suck air even when the resevior is full? Thanks One other thing I unplugged my temp alarm sensor and the alarm still went off. Could there be another temp sensor. But after unhooking the sensor I started to get the 2 beeps per minute alarm. But the constant alarm still went off even thow I unhooked the Temp sensor. Thanks Mako for your help!!!! Buy the way what is HX ?
 
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