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View Full Version : Engine temp/alarm question '99 350 Mag



Bryan Tuvell 33ZX
09-22-2001, 07:52 PM
Made a long trip today, about a 200 mile run, almost home cruising at 45 MPH I hear the alarm, look over, gauge is at 240, but didn't shut down on her own. I kill her.

(Alpha gen II drive) Gave a few taps on the thermostat housing, pulled the single brown wire off and it seemed to be the problem, the gauge would not read right, one time zero, one time 130 etc etc, finally after taking it on and off a few times it registered normal (175 degrees).

So does the engine only shut down when it is actually too hot? It would appear the gauge/sensor plays no part in that.

Also what does the 2 wire connection opposite the single brown wire do? Could I have maybe picked up a bit of trash that could have interferred with the sensor?
I plan to replace the sensor, any install tips?
Thanks in advance as always.
Bryan

Moody Blu'
09-24-2001, 11:55 AM
You should always keep your eye on the temperature and oil gauges
:rolleyes:
Unless you want install tips on a new engine.

Bryan Tuvell 33ZX
09-24-2001, 03:29 PM
Thanks Sky, but I won't need tips on what would be a warranty repair until after November 2004. :p
I was looking for a technical answer in reference to the alarm and exactly how the auto shut down works on the small block Mag engines and how it is wired..
Bryan

Hardonzi
09-24-2001, 06:59 PM
Bryan:I had no oil pressure on my gauge 2 weeks ago hauling at 60 mph..Thats right big 0-zero-nada-nothing but no alarms or shutdwn.My mechanic told me had that been for real u woulda known well before alarms sounded just by the pure sound of lifters clanking like a diesel truck.In fact he said take it out all u want get it to me soon, so i can replace the sensor..The alarms did not sound cause the alarms work off the computer on the motor not your gauges.I would say your alarms were justified,cause of your gauge and alarm.As for clogging,good chance thats all it is..Hammer it and EYEBALL THE GAUGE trim all the way down..Make sure its COLD though.. ;)

Moody Blu'
09-24-2001, 08:18 PM
Thats cool, but its hard to break bad habits(not looking at gauges)

Bryan Tuvell 33ZX
09-25-2001, 02:49 PM
Hey there Mad Poodle.... my understanding from a similar past problem with the new drive, when she truely gets to hot she does shut off, controlled by the ECM module is what I read.
I am still going to replace the sensor, easy job. I boated the next day all day without replacing the sensor and she was fine, maybe a fluke or maybe some trash got in there and flushed itself out.
The oddity was the gauge reading everytime I reset the wire to the sensor.
Thanks... see ya next May for sure!
Bryan

Forrest
09-25-2001, 03:30 PM
Bryan, don't you just love all of the back seat drivin'!!! :eek:

Bryan Tuvell 33ZX
09-25-2001, 04:42 PM
Forrest, I know I shouldn't bite but I will... Back Seat Driving?

Say hi to the better half for me... when you coming our way again?
Bryan

Shanghied Again
09-25-2001, 08:16 PM
Bryan, The engine will not shut, I clogged my cooler last year on a Island I moored at, I sucked up silt, The alarm went off at 220 and climbed I shut down. The engine can cool down quick. I back flushed the whole system and she has been fine since. Make sure you are not getting a partial clog. The only sensor that will shut your motor down is the knock sensor. If there is a shut down sensor for the temp its usally to late.

Murphy
10-10-2001, 07:56 PM
Just got back to the board after being gone awhile... when you install that sensor don't use any kind of sealant like teflon tape or grease. The sensor must be well grounded to work right. MerCruiser has a small entry in their service manuals about this in most cases.

Murph