boat stereo clicks off at low RPM

[boatuser99]

Hi,

I have a 18ft Grew Bowrider with a Mercruiser 4.3 stern drive. For some reason, the stereo clicks off when the boat is running at low RPM - it will work in Neutral (which is about 1100 rpm) but when I shift into forward it cuts off (at that point, without giving it extra throttle, the engine is running around 700 rpm.)

The radio works fine when the engine isn't running. The other devices that run off the battery seem to be functioning properly as well.

I have a new Interstate battery (bought at the end of last year) as well as a new alternator.

Someone told me that the radio runs off of the battery. The battery is then charged by the alternator. Is this true? To me, it looks like when the engine is running, the radio runs off the electricity generated by the alternator, which would explain why the radio cuts out at low rpm.

One other note is that my voltage gauge does seem to go down during low RPM i.e. dips below 10.

 

[bruceb58]

Measure the voltage at your battery while the engine is running at various RPMs. If that is around 13.5V, you have a voltage drop between your battery and your helm.

 

[boatuser99]

Thanks for the advice,

what has to be fixed if there is a voltage drop between the battery and the helm?

 

[bruceb58]

If your voltage measures good at the battery, I would do the following steps. You will need a long test lead and a meter. I make up my own test lead with a long wire and add alligator clips on the ends.

1) measure voltage between positive of battery and positive of your helm fuse bank.
2) measure voltage between negative of battery and negative of your helm fuse bank.

Do these tests with engine running and with engine off and ignition in the on position. Should be similar readings.

The measurements you get should be minimal. If they are greater than 0,5V or so, you need to check the engine connector and where the ground is picked up by the engine harness. Also need to check the connection at the starter if the drop is in the positive side. Could be either positive or negative that is causing your problem. That is why you do the #1 and #2 tests.