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Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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Have an alarm going off on my 5.7 mercruiser. Motor runs about

Customer Question

Have an alarm going off on my 5.7 mercruiser. Motor runs about 175 for the temp. Just replaced motor less then four running hours ago. New impeller and thermostat installed as I was putting back together. Have full gear oil in reservoir in engine compartment, and run around 40-43 psi on the engine oil. Alarm sounds as should when key is turned before start and once started it continues to sound, notice it's a real quick jump to 175° on the garage tho. What am I missing?
Submitted: 1 year ago.
Category: Boat
Expert:  Tan replied 1 year ago.
Hello. My name is***** get the engine serial number please?175*F is not over heating you are right on with temps. Operating temp is 175*F+/-5*F The oil pressure can cause an alarm also. You have eliminated lube and temp leaving only oil pressure. I would locate the oil pressure switch disconnect the tan/blue wire from the switch does alarm quit? The oil switch will be near the distributor or down by the oil filter. Does the alarm go off when you get some rpms up on the engine? If alarm quits we need to verify the oil pressure with a mechanical oil pressure gauge.
Customer: replied 1 year ago.
No rpms play no factor in the alarm on. Doesn't matter what rpm I'm at its still staying on
Customer: replied 1 year ago.
Can I put the mechanical oil gauge on with out dropping the oil?
Expert:  Tan replied 1 year ago.
Ok then the oil pressure switch is not working it is most likely plugged. This will make the alarm sound continuously. The alarm sounding continuously is over heat or no oil pressure. Locate the oil switch and unplug the tan/blue wire from the oil switch does the alarm go off? Yes the mechanical can be installed without dumping the oil. I want to verify that the oil pressure gauge is reading correct. I don't want to say the oil switch is bad till we have verified oil pressure. The gauge could be wrong and the oil switch is doing it's job telling us you have no oil pressure. We have to believe the audio alarm system is working. Do you follow what I am saying?
Customer: replied 1 year ago.
I believe so. I will have to get to the boat and try this and let you know
Expert:  Tan replied 1 year ago.
Ok that's fine. The oil sending unit # ***** is for the gauge. Audio sender is # ***** # ***** is where we need to disconnect the tan/blue wire. If the alarm quits remove that sender and install the oil pressure gauge in it's place. Do you have good oil pressure? Post back with findings and questions.
Expert:  Tan replied 1 year ago.
I will need the engine serial number to verify the correct part number for the oil switch.

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