Stero Help Please - Perplexed.

So I put a post up regarding when I get over around 1750 Rpm's the radio turns off and when I get below that it automatically turns back on - goes default to tuner, but comes on. The radio plays fine in accessory mode or idling/cruising below 1750 RPM - it plays as loud as you want.

So here is where it gets puzzling. I got it home and tried to replicate the issue and check the voltage output. I hooked up the fake lake and put the engine in neutral and reved it up with the radio on. No problem. So I engaged the prop and ran it up to about 2500 RPM and again no problem. The voltage meter read 13.4-13.6 at the highest level. I thought well maybe it was just having a bad day since I could not replicate the issue out of the water.

So I take the boat out today and low and behold once I get the boat above 1750 RPM it turns off. I put the boat in neutral in the water and revved it up and had no problems.

So the problem happens only when the boat is in the water proper engaged and above 1750 RPM - will play all day long below that and even with prop engaged so long as it is below 1750 RPM. Any ideas? Wired that something would cause this only in the water and moving.

Suggestions would be appreciated.

You have a tough one there.
I still wouldn't rule out voltage regulation and getting too much voltage so I would check the terminals directly at the alternator with a meter.
Next, I wouldn't trust the supply and ground. I would run a new 14-ga B+ and ground to the battery direct and definitely verify that its to the same battery or switch post as any amplification. Also, check the amplifier ground.
If those steps don't produce anything then strip the HU of all speakers, remote controls, RCAs, illumumination, remote turn-on lead or other inter-connections. Power and ground only. See how it behaves then. If it works fine under those conditions then reinstate one connection at a time. I know its primitive but simple isolation and elimination generally works.
There is a small chance that the HU is damaged, whether water damage or other, and that it fails when the voltage crosses a certain threshold, even though that voltage is normal. Look for any signs of corrosion or a white residue on the source unit.

David
Earmark Marine

It sounds like you have a floating ground. If you have voltage introduced on your ground line then it would drop the total voltage seen by the hu. For example, if at whatever rpm you see the issue put a 3volt noise signal on your grounding harness your hu would only see 10volts (13v-3v) which could be enough to shut it off. Make sure the ground on your hu is ran directly to the battery or to the ground on your largest amp and not to an assessory grounding strip or something of that sort.

I definitely see the logic of what wakebrooks is saying. If the HU ground was tied into an illumination circuit that was temporarly turned down and measured like a ground from all the parallel DC bulbs, or if other electrical components on a shared circuit with the HU did not have an acceptable ground you could get some unusual behaviors caused by an 'above ground' that would be confusing. That is all the more reason for the HU to have a heavier gauge dedicated supply and ground. Corrosive deposits from water exposure across traces within the HU could also create the same effect.

David
Earmark Marine

That makes sense - I did notice the cruise control backlite was on even when it was swtiched to the off position. After the install of the second amp they did rewire my head unit and I bet they tied it into ground for something else (perhaps the DC bulbs). Nonetheless I am going to have the installer run the ground and power wire directly to the distribution blocks I had installed for the amps. I have 4 GA to the blocks directly from the battery which should be sufficient to handle the load of a head unit.

I am going to also have the installer check the output of the alternator directly with a voltmeter to rule that out, but my hunch is the direct wiring should fix it.

Josh,
The issue that wakebrooks raised coincidentally with a recent HU rewire might have some real traction.

David
Earmark Marine

Originally Posted by wakebrooks

It sounds like you have a floating ground. If you have voltage introduced on your ground line then it would drop the total voltage seen by the hu. For example, if at whatever rpm you see the issue put a 3volt noise signal on your grounding harness your hu would only see 10volts (13v-3v) which could be enough to shut it off. Make sure the ground on your hu is ran directly to the battery or to the ground on your largest amp and not to an assessory grounding strip or something of that sort.

Good advice man!