Electrical system: amp draw and necessary upgrades, voltage dip to dashboard

[thedude]

Guys, I figured this was the best place to post this question due to its electrical nature.

Boat is a 2003 SANTE which is stock (stock tower and boat speakers, 2 clarion marine amps, dual batteries with stock switch). Engine is the excal 343 with stock alternator. Batteries are Deka and fairly new.

My issue: this spring I replaced my stock ballast system with (3) Johnson Ultra Ballast pumps. I wired them to the stock keypad using automotive style relays to operate the pumps, this system works great with one exception. While the boat is running, I can turn all of the pumps on and fill the ballast system, no issues there. The problem is when I go to turn the pumps off (one by one), the voltage to the dashboard varies and the dashboard cuts out for a half second, then kicks back on. The problem is it cuts off the perfect pass and speedo as well, causing the boat speed to surge and the speedo to not work until the boat is shut off, and then re-started.

I figure each pumps draws about 13-15A according to page 7 of the pump manual: http://www.johnson-pump.com/jpmarine...410_F4B-11.pdf

I believe what is happening is when I shut the pumps off, the voltage to the dash jumps to a level that is out of range of the dash components. Does this sound logical? What is the most economical way to solve this issue? I've read that increasing wire size could help, installing a capacitor, or upgrading the alternator could all help. I don't want to chase my tail on this.

I'm open to suggestions. Can anyone recommend a capacitor if that is the way to go? Would I need one for each battery?

Thanks guys!

[EarmarkMarine]

If you do not want to chase your tail then take concise measurements to begin with as to the exact momentary voltage at the dash under certain conditions. You first need to know precisely what is going on.
Let's say that the alternator adjusts to the load and once the load is gone it takes a moment to adjust back to a lower output. If that is the case then it could mean that the voltage is temporarily high enough to potentially do damage to solid state electronics. So I question the state of your voltage regulator. The inverse when you turn the pumps on would not surprise me. This situation does.
A very large stiffening capacitor may be used on a daily driver but can be a major problem on a boat where the capacitor is discharged and recharged with each storage cycle. Suddenly introducing an empty cap to a substantial current supply can eventually damage the cap at which time it becomes a liability to your charging system. You could try a more moderate capacitor at/closest to the items most affected.
You can never go wrong with increasing the wire gauge and lowering the resistance, especially on the ground side, to the dash helm buss and any high current devices. Make sure that with all this extra draw that the ground to the engine block and the supply from the alternator to the batteries is large enough now.
A Perfect Pass is known to be very voltage sensitive.
Once you have corrected any real problems, you might be able to isolate one battery that feeds the pumps with a solenoid that is triggered simultaneously with the pumps control switch. That would allow stability.

David
Earmark Marine

[thedude]

Thanks guys I got this all figured out. Following the lead of a member here who had a similar issue, I swapped out my pump relays for relays with a internal diode. That simple change has everything working perfectly now. I'm glad it only cost me $45 worth or new relays instead of a larger issue!

[Mikeski]

The 2003 boats are also notorious for having undersized wires between the battery and dash main fuse block. If it were my boat I would upsize those to #4 or #6 wire, I believe the factory uses #8 which is probably fine from an ampacity standpoint but drops too much voltage when loaded.