Mercathode for dryrack

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Mercathode for dryrack

Postby stitchsc » Thu Mar 28, 2019 5:24 am

Howdy all!

Just found out recently that my Mercathode (Bravo3) is draining a battery almost dead after sitting (drystacked) for only one month. It has done this twice now and I am in the initial stages of researching / testing / checking things out and wanted to see some thoughts out there.

The boat is dry stacked but when we launch(1-2 times/mo) it will sit in the water (Marina) for 2-3 days each time. Brackish to salt water use.

Opinions i have heard so far....

1. I have read in other places that a drystacked B3 can go without the mercathode (I.e. Unplug the system from power). My mechanic says i am insane if i do that.

2. Another theory is my battery is just old / week and the power drain is not enough to kill a battery (Optima Blue - going on 5 yrs old but holds a charge very well without mercathode powered up, no other signs or issues)

3. The mercathode is shorting out and i need to have the dealer test / inspect it.

Thanks for any thoughts!
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Re: Mercathode for dryrack

Postby Chris_in_Texas » Thu Mar 28, 2019 5:12 pm

Easiest fix it simply run it thru the battery switch. That way when you turn off your power you disable the system. I am not sure what the current draw of the system is but say 0.1A that would be about 72Ah over the course of a month of time. For the bluetop 34M that battery has a capacity of 50Ah so that would explain it draining it to zero, which is quite hard on the battery. If it were myself I would simply move it from the direct connection to the battery (or battery side of the switch) to the switched side of the battery switch. I had the same issue on my VP system as well on my bow rider that was stored on land as well. However not having to deal with salt water with that boat I disconnected it all together.

I know the B3 can be sensitive to corrosion, so I would want it connected and make sure that the anodes are checked from time to time as well. If you have zinc anodes, remember that each time the boat comes out of the water a non porous layer will dry on the anodes, it will render them useless until they wire-brushed to remove this prior to re-immersion. ;)
Thanks, Chris

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Re: Mercathode for dryrack

Postby stitchsc » Thu Mar 28, 2019 7:27 pm

Hey Chris!
I was hoping you would chime in on this and thank you.

I am on the same line of thinking as you (post perko switch) since the 2-3 days it is in the water we are on it and the switch is on. I did notice a few hours ago the orange line(+) going to the unit attached to the outdrive is frayed and wire is exposed a bit. Doesn't explain the power draw while on the dry rack, but does make me question the systems integrity all together. May have to have the dealer look at it and test it.

Orrrrr leave it unplugged and inspect the B3 and anodes each time for a few months to get a feel for everything.

:( ug :(

~IF~ i did leave it off all together am i correct in assuming the normal anodes would still be worn down before the outdrive?

Thanks for the wire brush suggestion...is that the same for Aluminum anodes? Either way.....easy enough to do before each launch!
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Re: Mercathode for dryrack

Postby Chris_in_Texas » Sat Mar 30, 2019 11:20 am

That is the theory that the zincs are the least noble metal between the outdrive and boat, so they should wear first. That's not to say that will happen in that exact way. That was some of the reason that the B3's have a bad rap for corrosion. The Mercathode is in response to that. I would keep the system running if it were me, is 2 or 3 days going to eat the drive away, most likely no, but over time it could.

According to Navalloy the alum ones won't require the brushing and will work right away going from wet to dry and back to wet. They don't require any type of wire brushing.

https://performancemetals.com/
Thanks, Chris

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2007 - Regal 3060 - Twin VP 5.0OSi - XDP - SOLD
2002 - Crownline 230BR VP 8.2GSiPEFS - DP-SM - SOLD
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Re: Mercathode for dryrack

Postby Mischief Managed » Sun Apr 07, 2019 8:04 pm

I think there's either something wrong with your Mercathode or the wiring for it, or there's some other current draw. I'm pretty sure it should not draw any current when dry racked, there's no water for the current to flow through.
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Re: Mercathode for dryrack

Postby gofast24 » Sun Apr 14, 2019 10:26 am

Mischief Managed wrote:I think there's either something wrong with your Mercathode or the wiring for it, or there's some other current draw. I'm pretty sure it should not draw any current when dry racked, there's no water for the current to flow through.

Agree, other than the "electronic" module that is controlling the system possibly draws current? I bought a AC/DC current clamp on meter (a few years ago, $38 Amazon) want to test the inrush current of both HVAC units (one 15 AMP breaker tripping occasionally on our aft 16k BTU unit). New clamp on will read DC current down to a 2 amp DC full scale. Maybe test the current draw to the unit and compared to specifications ?
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