View Full Version : False Overheating constant alarm on 1996 Mariner 135HP .. what has failed?

08-02-2019, 02:56 PM
Not finding what I need in search so.. maybe one of you experienced lads can point me in the right direction

This just occurred after I thought the engine oil tank was slightly leaking and I tightened the cap only to have the top section separate from the sides. The system being under slight pressure proceeded to dump oil all over the carbs which took an hour to clean up with degreaser and hosing off. Anyway, after epoxying the cap back together, the next rip out, the alarm horn came on constant when the key was turned on instead of just the initial beep.
So my initial troubleshooting was focused on the oil system until I discovered that the constant alarm is for overheating.

On land with cold engine , turning on key results in continuous alarm from control box

On the right side of engine block (as viewed from rear) there are three tan-and-blue striped wires going to a junction block. One(1) of those tan-blue wires comes from the Warning Module (on left side of block), another (2)comes from the temp sensor on the right cylinder bank (as viewed from rear), an the 3rd runs into the main harness .

Tests with connected:

(1)+(2)+(3), then turn on key, the constant alarm occurs.
If I only leave attached(2) the sensor tan-blue + (3), no constant alarm but no initial beep either.
If I only leave the (1)warning module tan-blue attached + (3), get the constant alarm again.
with none attached, get nothing
with (3) only attached get nothing
with (1) Warning module + (2) sensor attached, get nothing

So from these tests, can you tell what is faulty ... the temp sensor or the warning module or potentially both?

Also, why does the left hand temp sensor(when viewed from rear) have both a ground wire which is immediately grounded beside it and a tan wire coming out of it and the tan wire runs over to the right side and into the harness???

Greatly appreciate any assistance in helping me identify the culprit(s).

09-01-2019, 11:03 PM
Update...tried swapping in a used but supposedly good warning module and it made no difference.

anyone help troubleshoot this please???

09-02-2019, 09:49 AM
So, what is your actual problem? A short and to the point description will get you more results.

09-02-2019, 07:47 PM
Chris, as it says after the first paragraph..

"On land with cold engine , turning on key results in continuous alarm from (remote) control box"

As you know, that is not normal...should just be a short beep to indicate system is functioning.

Reminder describes troubleshooting to date in hope that it might help with someone else supplying a solution


09-02-2019, 07:51 PM
Start looking for a short to ground.