Mysterious Mercathode System

[Dave S]

Since my Mercathode had voltage going to it regardless of the battery position on the GUEST Switch, then I believe I am "hard wired" to one of the batteries somehow thru the wiring harness in the panel. But what is a bit baffling to me are the various voltage readings I get when moving the switch around to the various positions. If the mercathode was connected directly to the battery terminals, I wouldn't have seen any voltage flucuation since the switch would have been removed from the equation. So why did I get the various voltage readings and would it be possible that asimpkinsjr is wired incorrectly into the wiring harness? Unfortunatly (for me) you guys are a bit more informed on electrical things than I am but would it be possible to come up with a simpler explanation here that might explain my situation as well asasimpkinsjr situation? Or maybe you have done that and I am just not smart enough to understand. :smt017

 

[MLauman]

Since my Mercathode had voltage going to it regardless of the battery position on the GUEST Switch, then I believe I am "hard wired" to one of the batteries somehow thru the wiring harness in the panel. But what is a bit baffling to me are the various voltage readings I get when moving the switch around to the various positions. If the mercathode was connected directly to the battery terminals, I wouldn't have seen any voltage flucuation since the switch would have been removed from the equation. So why did I get the various voltage readings and would it be possible that asimpkinsjr is wired incorrectly into the wiring harness? Unfortunatly (for me) you guys are a bit more informed on electrical things than I am but would it be possible to come up with a simpler explanation here that might explain my situation as well asasimpkinsjr situation? Or maybe you have done that and I am just not smart enough to understand. :smt017

BOTH.........13.85 volts and steady

Battery 1..............12.70 volts initially and then slowly dropping

Battery 2...........13.17 volts and steady

OFF............13.19 volts with up and down fluctuations

With the switch in the #2 or OFF position, the mercathode is enjoying sole (unshared) use of the power from battery #1 (the 13.17-19 reading). When you switch to battery #1 you are probably placing an additional load on it from some other source (radio, light, etc.) that is drawing it down slightly (the 12.7v reading). The BOTH setting is self-explanatory as it benefits from the combination of the 2 batteries.

It makes sense to me but I don't know if my explanation does. :smt017

 

[Dave S]

Then if battery #1 would fail for some reason, could I conclude that by placing my switch in the both or number 2 position I would automatically have power again for the mercathode and anything else hardwired to battery 1?

 

[MLauman]

Then if battery #1 would fail for some reason, could I conclude that by placing my switch in the both or number 2 position I would automatically have power again for the mercathode and anything else hardwired to battery 1?

Yes and No! Having the switch in the BOTH setting is just like using jumper cables between the batteries, so it would power anything directly connected to either battery (assuming one of them is good). But with the switch in Batt2 position, the #1 battery (and everything DIRECTLY connected to it) becomes totally isolated.

The only way to power your mercathode with a dead #1 (using the switch) is to put it on BOTH.

 

[asimpkinsjr]

Since my Mercathode had voltage going to it regardless of the battery position on the GUEST Switch, then I believe I am "hard wired" to one of the batteries somehow thru the wiring harness in the panel. But what is a bit baffling to me are the various voltage readings I get when moving the switch around to the various positions. If the mercathode was connected directly to the battery terminals, I wouldn't have seen any voltage flucuation since the switch would have been removed from the equation. So why did I get the various voltage readings and would it be possible that asimpkinsjr is wired incorrectly into the wiring harness? Unfortunatly (for me) you guys are a bit more informed on electrical things than I am but would it be possible to come up with a simpler explanation here that might explain my situation as well asasimpkinsjr situation? Or maybe you have done that and I am just not smart enough to understand. :smt017

BOTH.........13.85 volts and steady

Battery 1..............12.70 volts initially and then slowly dropping

Battery 2...........13.17 volts and steady

OFF............13.19 volts with up and down fluctuations

With the switch in the #2 or OFF position, the mercathode is enjoying sole (unshared) use of the power from battery #1 (the 13.17-19 reading). When you switch to battery #1 you are probably placing an additional load on it from some other source (radio, light, etc.) that is drawing it down slightly (the 12.7v reading). The BOTH setting is self-explanatory as it benefits from the combination of the 2 batteries.

It makes sense to me but I don't know if my explanation does. :smt017

How do you explain the merthacode on Dave's boat having power with the switch in the off position? when the schematic shows the mercathode wired to guest switch position one.

 

[asimpkinsjr]

On my boat the current situation is that the mercathode only seems powered when the guest switch is in the both position (evidenced by testing the dealer did on the controller), something that we now are thinking could be a result of a miswire at the guest switch

There is no way to wire (or miswire) the switch to produce that result. The only plausible explanation for this condition would be a (highly) defective switch - could the knob be out of sync?

what Im questioning is how on Dave. S's boat is getting power to the mercathode when the guest switch is in the off or 2 position based upon the wiring diagrams from the owners manual which an excerpt of which you have posted. Im not sure if you are explaining that it makes sense to you based upon SRs diagrams or not...

Dave S's results are exactly as they should be per the diagrams and my boat is the same way. The effect of connecting the mercathode wire to the batt1 terminal on the switch is exactly the same as connecting the mercathode directly to the #1 battery. It makes no difference which position the switch is in.

The dealer thinks that the feeder lead and the batt1 or 2 being transposed my explain it...I just gotta wait for the yard to put the door in the shrink to be able to check it out

 

[MLauman]

How do you explain the merthacode on Dave's boat having power with the switch in the off position? when the schematic shows the mercathode wired to guest switch position one.

Don't look at it as being wired to switch position one - rather the mercathode is wired to switch terminal one. The Batt1 and Batt2 switch terminals are NOT affected by the switch selector position.

Assuming a properly wired switch and charged batteries:

The Batt1 switch terminal is connected DIRECTLY to the battery post. The Batt1 switch terminal is ALWAYS HOT. No matter what position the switch selector is in, the Batt1 switch terminal is ALWAYS HOT. Therefore, anything that's connected to the Batt1 terminal is ALWAYS POWERED. Again, the switch can be in any other position, including OFF and it has no effect on the Batt1 swwitch terminal.

The same applies to the Batt2 switch terminal.

The FEED switch terminal is the only one that is affected by the position of the switch selector.

Hope this helps clear it up a bit.

 

[MLauman]

On my boat the current situation is that the mercathode only seems powered when the guest switch is in the both position (evidenced by testing the dealer did on the controller), something that we now are thinking could be a result of a miswire at the guest switch

The dealer thinks that the feeder lead and the batt1 or 2 being transposed my explain it...I just gotta wait for the yard to put the door in the shrink to be able to check it out

Sorry, but I stand by my earlier statement - that scenario cannot be created with a properly functioning switch and charged batteries no matter how it is wired. No matter how you mix up the 3 cables (Batt1, Batt2 & Feed), one of the switch positions (1 or 2) would have to provide power to the mercathode (as well as Both).

With the Batt1 and Feed wires swapped (and the mercathode wired to Batt1) this is what you get:

Switch   Mercathode   Boat

   1         Yes      Yes

   2         No       No

   B         Yes      Yes

With the Batt1 and Feed wires swapped (and the mercathode wired to Batt2) this is what you get:

Switch   Mercathode   Boat

   1         Yes      Yes

   2         Yes      No

   B         Yes      Yes

With the Batt1 and Feed wires swapped (and the mercathode wired to Feed) this is what you get:

Switch   Mercathode   Boat

   1         Yes      Yes

   2         Yes      No

   B         Yes      Yes

Swapping Batt2 and Feed wires would have the same affect - just swap the 1 & 2 switch settings.

There is no wiring scenario where the mercathode can ONLY get power with the switch set to BOTH. Further, if the wires are swapped as suggested by your dealer then your boat's main power would be affected as well. One of the two switch settings (1 or 2) would provide no power to the boat - would be like having it in the Off position.

Now if one of your batteries was dead and the wires were swapped then you could have the situation you describe. But again, it would affect the boat's main power as well.

 

[thunderbird1]

You may want to go to www.mercurymarine.com and ask for their publication 90-881813 01 it is titled Marine Corrosion Protection Guide. It will teach you everything you want to know about how the system works and more important how to check that it IS working while the boat is in the water.

Excellent suggestion Stray Cat! Mercury Marine mailed me the informative document at no charge. So here is what the Guide has to say on page 10.

"The power supply for the MerCathode System is provided by the engine wiring harness. If your boat is equipped with a battery switch, the switch must be left in the "On" position when the boat is moored in order for the system to provide protection.

To allow the battery switch to be placed in the "Off" position while boat is moored, remove and discard the red-purple power supply lead for the "+" terminal of the controller and connect a separate wire between the "+" terminal on the controller and the positive (+) battery terminal. This lead must be fitted with a three-amp fuse, placed within six inches (15 cm) of the positive battery terminal."

Given this information, I suspect many of us who keep our boats in the water (and who turn the battery switch "Off" for safety when not using the boat), have had no Mercathode protection. :smt021

The Guide also confirms the the Mercathode system should use little battery power. "The Mercathode controller output is limited, by design, to approximately 200 mA to avoid a rapid drain of the boat's battery."

 

[Dave S]

Given this information, I suspect many of us who keep our boats in the water (and who turn the battery switch "Off" for safety when not using the boat), have had no Mercathode protection. :smt021

I still think you need to check the voltage from the Mercathode Power wire first to see if you have voltage with the switch off. Mine did and I have to believe that Sea Ray wired mine the correct way (and possibly didn't with yours? :smt021 ) Don't forget that Merc's instructions are intended for everyone but each boat builder has to do their own install of the Mercathode System. Some builders may get it right and some may not. Also remember that nothing (bilge pumps, mercathode, radio memory, etc) has a hardwire running to the battery as suggested by Mercury. Instead, they tie everything into the battery wiring behind the panel containing the switch and the breakers.

 

[thunderbird1]

Dave: Once I get my boat back (I'm having a second windshield wiper and beefed-up Mercathode system installed), I'll check the voltage. Thanks for the suggestion.

Any idea whether Sea Ray installed a 3-amp fuse on your boat as specified by Mercury?

 

[Dave S]

Any idea whether Sea Ray installed a 3-amp fuse on your boat as specified by Mercury?

I don't know. I never pulled the power panel to check the wiring or tried to follow the wiring to see if it's in the engine compartment somewhere.

 

[Stray Cat]

I am thinking of adding one of these to my tool kit: http://www.boatzincs.com/corrosion-reference-electrode.html

With the boat out of the water, I would measure from the swim platform down to each drive. (I can't see my drives when the boat is in the water.) Then I'd make a mark on the tester wire to make certain I have it located in the right location. This is the best way to assure the Mercathode system is working and your hardware is "protected".

 

[Bridog]

Wow I just started reading this and now my head hurts :wink: So bottom line.. If you have a newer SR and it has a Bravo 3 it comes standard from SR with a mercathode. If your boat has twins it should have 2 mercathodes(again standard from SR) and the power to them is always on despite what posistion your battery is on... right?

 

[Dave S]

Wow I just started reading this and now my head hurts :wink: So bottom line.. If you have a newer SR and it has a Bravo 3 it comes standard from SR with a mercathode. If your boat has twins it should have 2 mercathodes(again standard from SR) and the power to them is always on despite what posistion your battery is on... right?

That's correct Brian. Some of us (including me) have gone the extra mile and had a second Mercathode installed as well. When you get your 300, just keep an eye on the out drives. did you have a B3 on your old 260? If you did and didn't experience corrosion issues then your 300 should be fine.

 

[Bridog]

Thanks for clearing that up Dave.

 

[asimpkinsjr]

You may want to go to www.mercurymarine.com and ask for their publication 90-881813 01 it is titled Marine Corrosion Protection Guide. It will teach you everything you want to know about how the system works and more important how to check that it IS working while the boat is in the water.

Excellent suggestion Stray Cat! Mercury Marine mailed me the informative document at no charge. So here is what the Guide has to say on page 10.

"The power supply for the MerCathode System is provided by the engine wiring harness. If your boat is equipped with a battery switch, the switch must be left in the "On" position when the boat is moored in order for the system to provide protection.

To allow the battery switch to be placed in the "Off" position while boat is moored, remove and discard the red-purple power supply lead for the "+" terminal of the controller and connect a separate wire between the "+" terminal on the controller and the positive (+) battery terminal. This lead must be fitted with a three-amp fuse, placed within six inches (15 cm) of the positive battery terminal."

Given this information, I suspect many of us who keep our boats in the water (and who turn the battery switch "Off" for safety when not using the boat), have had no Mercathode protection. :smt021

The Guide also confirms the the Mercathode system should use little battery power. "The Mercathode controller output is limited, by design, to approximately 200 mA to avoid a rapid drain of the boat's battery."

Interesting...this is exactly what ive been saying for some time is the behavior exhibited in my boat....

 

[thunderbird1]

Wow I just started reading this and now my head hurts :wink: So bottom line.. If you have a newer SR and it has a Bravo 3 it comes standard from SR with a mercathode. If your boat has twins it should have 2 mercathodes(again standard from SR) and the power to them is always on despite what posistion your battery is on... right?

I agree with Dave that having the beefed-up Mercathode system installed (adding two anodes @approximately $250) is good insurance. My boat is being upgraded this week. Dave's boat is wired so that his Mercathode system is always on. My boat is wired so that the Mercathode is on only when my battery switch is turned on. I'm not sure we've determined yet which configuration is the "standard" Sea Ray install.

 

[Piringa]

Hi, Sorry if I am re-asking an answered question but here goes... is my 240 as spec'd below supposed to have the mercathode system? Where would it be mounted if I have one?

 

[jason78]

Hi, Sorry if I am re-asking an answered question but here goes... is my 240 as spec'd below supposed to have the mercathode system? Where would it be mounted if I have one?

According to the SR sales brochure it does not show it listed as being included on your year/model. I am not positive on the 5.7EFI where it would be located but it would be toward the top of the engine and will most likely be a blue module with 4 leads about the size of a cigarette pack that says "MERCATHODE" on it.

If it makes you feel any better, since you have a Bravo 2 it is not nearly as big of a deal since you only have a single prop but it would still be nice to have if you have a Stainless Steel prop.

No Mercathode on a slipped Bravo 3 will mean a certain death from corrosion.