Battery Alarm but batteries fine

[John Paul]

one of our two engines will not start; battery alarm but all batteries new and connections clean. Emergency start bridge changes nothing; no power when turn key to start engine over battery alarm. Is there a major fuse somewhere? All power otherwise is fine to all areas and accessories.

 

[Bt Doctur]

Do the gauges "come alive" ?
Shifter in Neutral ?

 

[John Paul]

Yes. The gauges come alive and show all OK except the battery for one of the two engines. I did check to make sure in neutral.

 

[Bt Doctur]

Assuming it was running correctly and you didnt do any work on it then suspect the battery connected to that engine. Also check the connections at the starter and the block
Being a twin you should have independent systems with a battery for each engine.
post a pic of the engine, if you dont know what/where a slave solenoid is.

 

[barros1389]

If you have an MPI, check to see if you have a 50amp fuse on the top of the engine. Mine appears to have a red button that trips the fuse. When it's tripped there is a little yellow arm under the fuse that needs to be reset. Otherwise it's most likely the starter fuse. I've tripped both at various times. Getting to my starter fuse is impossible. I had a friend merc mechanic replace it for me blindly because you can't see anything at the back of the engine.

 

[barros1389]

If you have an MPI, check to see if you have a 50amp fuse on the top of the engine. Mine appears to have a red button that trips the fuse. When it's tripped there is a little yellow arm under the fuse that needs to be reset. Otherwise it's most likely the starter fuse. I've tripped both at various times. Getting to my starter fuse is impossible. I had a friend merc mechanic replace it for me blindly because you can't see anything at the back of the engine.

Also check that your safety switch up at the helm isn't tripped.

 

[John Paul]

If you have an MPI, check to see if you have a 50amp fuse on the top of the engine. Mine appears to have a red button that trips the fuse. When it's tripped there is a little yellow arm under the fuse that needs to be reset. Otherwise it's most likely the starter fuse. I've tripped both at various times. Getting to my starter fuse is impossible. I had a friend merc mechanic replace it for me blindly because you can't see anything at the back of the engine.

Thanks. The 50 amp fuse on top of the engine is not tripped so it may be the starter fuse. The gauge shows low voltage Fault number 209. I will upload photos.

 

[John Paul]

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Thanks. The 50 amp fuse on top of the engine is not tripped so it may be the starter fuse. The gauge shows low voltage Fault number 209. I will upload photos.

 

[John Paul]

Dual Merc 350s. I do not see the starter.

 

[Bt Doctur]

click to enlarge
the off white square plastic block is the 90A

 

[Bt Doctur]

For a quick test if its blown, check for 12v at the orange alt output wire

 

[John Paul]

Turns out the starter fuse was not blown; merely corroded. Once we replaced that fuse and cleaned all the wires of corrosion, everything worked well. Interestingly, the power gauge showed plenty of amps getting to the engine until the key was turned to start the engine (to power the starter). Then the amps dropped.

 

[John Paul]

 

[Korkie]

Did you check the other motor as well?