Mercruiser 7.4L MPI Low Coolant Temp Alarm

Pete Williams

New Member
Oct 5, 2022
1
Boat Info
Regal 2660, 1998
Engines
Mercruiser 7.4L MPI
Wondering if anyone can help.


I’ve got a 1998 7.4L MPI/MEFI3 Mercruiser. Last year it was running fine, but was badly corroded and required a rebuild, which was completed recently.


When I tried to start her up, after about 10-15 seconds, I get an alarm. 1 Second on, 3 seconds off. Goes on forever.


The Mercruiser computer has been connected to it and at first was showing alarms from all sensors, then after a while, only showed alarm #14, low coolant temp. Very odd, as it would always be cold at start-up. Have run it up to temp in idle-1,700. Alarm stays on.


I’ve tried a new sensor, and have checked wire resistance is OK.


Any ideas???
 
Is this the temp sensor (ECT) with a multi-wire plug? Or the one that has a single post terminal and uses the engine for ground? On my MPI there's two sensors and both are in the thermostat housing: one sender with a post for the gauge, and the other which has a connector is a temp sensor. Where are your sensors located?

Assuming the alarm is because it thinks the temp is zero when it should be ambient temp at start-up
 
Not sure what scanner you are using but that mefi 3 is about as dumbed down as they get. You should be able to see the values of what it is capable of doing, see if they are in the normal range.

It only alarms for a few things, overheat, no oil pressure, low drive fluid. Disconnect those 1 at a time till it stops
 

Forum statistics

Threads
112,950
Messages
1,422,861
Members
60,932
Latest member
juliediane
Back
Top