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    Engine Alarms-gctid369994

    Hi folks! I have a 2000 4788 with 6BTA5.9M3/370's. While cruising home on the weekend, I decided to open up the throttles to the WOT of 3000 revs. I got to max out at 2900 admittedly into a headwind and ran for about 5 mins and both Coles Hersee buzzer/light alarms came on at the same time. After some anxious moments, I throttled back to idle and after 20-30 secs, both lights/buzzers stopped. During that time and at speed, the oil and coolant gauges were all in normal ranges. I had a look in the engine room at idle and things seemed normal, so put the boat back on the plane at 2500 revs and proceeded for about 10 mins. I then tried again for WOT and after another 5 mins the Port buzzer/light alarm came back on. Again, temps etc were not out of the normal range (185deg coolant and about 37 oil pressure).

    I've had the alarms go off about a year ago, but that was due to faulty alternators. Changed those, and the problem went away. The s/b alarm/light would not activate prior to start, but that turned out to be a faulty oil pressure switch that wouldn't close and once that was changed out, the alarms activated as per normal just prior to engine start.

    I put out a query on Boatdiesel.com and got the following response

    "So what kind of alarm system do you have? Cummins factory is a printed circuit board that looks at sender readings, then decides whether to alarm. No switches used. Boatbuilders often build their own systems usning dedicated switches. To make sense of your issue, need to know what kind of system you have."

    I searching the boatdiesel website, I found Cummins Harness Wiring Diagrams which would suggest there are 4 sensors?? that go to an electronic module - Water in Fuel, Low Voltage, High Temp, Low Oil. I can't see where the Coles Hersee module connects into the system, but there is an "Alarm Reset" switch? in the diagram. That Oil Pressure switch must be in the circuit somewhere as well given the lack of closing issue outline above.

    Anyway has anyone experienced a similar issue or know the electrics to point me in the right direction?? Assuming that Bayliner are using the Cummins wiring systems, I would imagine they have added the after market Coles Hersee alarm unit. Where is the Instrumentation "Electronic Module" located for example - one each for the PH and Flybridge??

    Any assistance would be much appreciated. Many thanks. Cheers
    John H
    Brisbane QLD Aust
    "Harbor-nating"

    2000 - 4788/Cummins 370's

    #2
    What is suggested minimum oil pressure for your engines? I know Mercruiser 5.0 normal range is 40-80 PSI. I usually see 45 PSI only at idle, anything over 1200 RPM and my oil pressure climbs to 70 PSI. Last year I had low oil pressure buzzer go off on me although gauge was showing normal pressure. Turned out buzzer is using a different pressure sender than a gauge and the wire terminal was corroded. After cleaning out contacts, warning buzzer issues have stopped from occurring.

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