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Charles
Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 3343
Experience:  US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
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Motor goes into guardian mode getting a 6 beep alarm had it

Customer Question

Motor goes into guardian mode getting a 6 beep alarm had it to a merc mech said low voltage was the only code he read changed batteries still same problem
JA: Sometimes things that you think will be really complicated end up being easy to fix. The Marine Mechanic I'm going to connect you with knows all the tricks and shortcuts. Tell me a bit more about what's going on so the Marine Mechanic can help you best.
Customer: Motor will not go above 3000rpm without activating guardian mode
JA: Is there anything else the Marine Mechanic should be aware of?
Customer: Motor seems to trim down while running without hitting power trim down button
Submitted: 3 months ago.
Category: Boat
Customer: replied 3 months ago.
Motor is a 2008 Mercury 4 stroke Efi 75hp
Expert:  Charles replied 3 months ago.

Hello, my name is***** will assist you.

Expert:  Charles replied 3 months ago.

Do you have a multimeter to do some testing?

Customer: replied 3 months ago.
Okgreat
Customer: replied 3 months ago.
Not with me
Customer: replied 3 months ago.
I have one at work but that's not going to help
Expert:  Charles replied 3 months ago.

No worries. This is whatI need you to test. With the key off, test the voltage that is at the starter solenoid. Then with water to the engine start it, measure the voltage again, it should have gone up slightly. Raise the RPM to 2000, then test the voltage again, if it is not going up to at least 14V DC, test the voltage that is coming from the stator, it is in AC, if it is producing about 16V AC, it is good, the voltage regulator has failed, replace that and the alarm will stop beeping.

Customer: replied 3 months ago.
Ok I did test the charging system last week with a battery tester and I was getting around 15 on the tester
Customer: replied 3 months ago.
I will bring home a multimeter tomorrow and try it the voltage regulator is located where about on the motor as you can tell I'm no boat motor mech I purchased the boat 3 years ago with no motor manual
Expert:  Charles replied 3 months ago.

Its actually part of the alternator on this engine. You would have to replace the Alt. Getting 15V is setting off an over voltage code.

Customer: replied 3 months ago.
Ok the merc dealer read a low voltage alarm code, to clarify I used a 100 amp battery tester with a charging system test option don't know how reliable it is
Expert:  Charles replied 3 months ago.

Either one will set off the code and cause the system to go into guardian.

Also make sure that there is voltage going to the post of the Alt with the key off. There is a 100A fuse between the Alt and the starter solenoid.

Customer: replied 3 months ago.
Ok so this motor doesn't have a rectifier or stator just a alt is that correct or does it have a three
Expert:  Charles replied 3 months ago.

That is correct. it has an Alt just like your truck. For some reason, I was thinking two stroke.

Customer: replied 3 months ago.
Ok should I so should I test the same way you originally stated
Expert:  Charles replied 3 months ago.

For the running test yes. Make sure that you have the 12V on the post of the Alt also before starting the engine. If may be a blown 100A fuse harness.

Customer: replied 3 months ago.
Ok
Expert:  Charles replied 3 months ago.

Let me know how it turns out.

Customer: replied 3 months ago.
Ok will do if it doesn't cost me LOL ?this method will still test the voltage regulator you touched on in the beginning
Expert:  Charles replied 3 months ago.

Yes, the running test is still the same. You will just need to test it at the Alt and also at the starter solenoid.

Customer: replied 3 months ago.
Great just checking, thanks if this works it beats spending another 100 for the computer diagnostics to be told to buy 230$ worth of batteries that didn't fix the problem. I appreciate your help. My kids will be appreciative also they are missing some quality crabbing and fishing. Thanks agai
Expert:  Charles replied 3 months ago.

Your very welcome. I feel that all of this should have already been checked by the guy that scanned the engine. I would have.

Customer: replied 3 months ago.
You are possible a more thorough mechanic than the shop I took it to. We shall see I never did mention that the motor runs great in the driveway just crappy on the water hopefully it's just a alt or voltage reg. There response was this motor runs great( on land but that ain't much help on the water) have a good night thanks again
Expert:  Charles replied 3 months ago.

Your very welcome.

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