Electrical Systems

Batteries And Their Differences

12 Volts – Deep Cycle/Crankingbatterysrm-29

  • Marine Cranking Amps (MCA): 845
  • Reserve Capacity: 210 minutes
  • Warranty Months: 30 months
  • Dimensions: 13″ x 6-3/4″ x 10″
  • Weight: 61 lbs.

12 Volts – Crankingbattery24m-rd

  • Marine Cranking Amps (MCA): 625
  • Reserve Capacity: 95 minutes
  • Warranty Months: 24 months
  • Dimensions: 11″ x 6-7/8″ x 9-1/2″
  • Weight: 38 lbs.


Zero maintenance. The battery is a completely sealed, gas-recombinant battery. This means that you never need to add water. This also means that you won’t be faced with the performance-robbing corrosion of most batteries.
Unsurpassed safety features. The electrolyte within an Optima is completely absorbed, there is no free acid to leak or spill. The Optima can be operated in any position without risk of leaking or spilling.
Unequaled vibration resistance. Vibration is one of the leading causes of failure with a flat plate battery, not so with this type. The plates within a gel type are tightly wound and pressed into the case so that they can’t move or break.
Long shelf life. The Gel can sit up to two years, unused, and still be as good as new. (A top off charge is recommended after one year.)


The number one piece of equipment needed is a good test light. Hook one end to any ground and check for 12volts on any wire or connection. Hook the end to positive (say on the battery) and check for any ground.
This tool will save you hundreds of dollars in repairs, without it you will have a very difficult time finding electrical problems, electricity is invisible and you will be guessing on everything unless you are able to use a test light. Buy one and keep it on board.Just because you don’t know how to use it doesn’t mean someone else won’t, the same applies for a good complete $100.00 tool box keep them in good shape and maybe your friends can help you out!
Start with the battery, check with the test light make sure everything is working right then attack your problem with the light in the same manner.

Some Wiring Basics

Standard colors for boats since 1980 are as follows,
  • heavy red 10 gauge (main battery)
  • heavy black (main ground)
  • purple (ignition)
  • yellow (starter solenoid)
  • grey (tachometer)
  • brown (temperature)
  • blue (oil pressure)
  • brown with stripe (alarm)
  • pink (fuel sending unit)
  • yellow (blower)
  • brown (bilge pump)
  • grey (navigation lights)
  • heavy green (bonding wire)
  • red (misc electrical ad ons , vhf , depth finder, stereo, radar, power supplies)

Common Problems

  • Check to see that the acid (electrolyte) level is up to the plastic liner inside holes and the fully charged specific gravity is 1.25 to 1.30 in each cell . (A tester can be purchased for less than $6.00)
  • Be sure that the top surfaces stay clean and dry or they will slowly discharge the batteries.
  • Check that all connections are tight with a pair of pliers or wrench, finger tight is not good!
  • Check to see if the engine cranks properly for 10 seconds with each battery alone, ground the ignition coil wire to a safe place and check for any gas fumes prior to checking, then crank the engine over so it won’t start but only turn over.
  • Check that all the cables are in good condition and the connections are clean and sealed from moisture.
  • Fasten all batteries down really good , they can cause a major disaster if they come loose in bad sea condition, fire can result.
  • Replace any batteries over 4 years old , it only leads to trouble.

Wiring & Connections

  • Check all battery switch connections to make sure there is no corrosion building up behind the switch.
  • Make sure all fuses have clean, tight, sealed contacts , use electrical tape sealer on all connections and replace connectors before they cause you problems.

Alternator & Starters

  • Check that with the with engine running and the batteries fully charged, and a 1 or 2 Amp load on system (a bilge pump or blower turned on), voltage to batteries is 13.9 to 14.4
  • Volts — and the voltage remains constant as more loads are turned on.
  • Make sure external connections are clean, sealed from moisture, and positive terminals are covered and alternator drive belt(s) are tight and in good shape no cracks or frays.
  • Listen for any strange bearing noises that might indicate upcoming problems from the alternator.
  • Watch for any signs of leaking water coming from exhaust manifolds and risers which are usually the number one cause of the starter solenoid being corroded and malfunctioning.
  • Keep the bildge dry from any water supply , this is the number one reason why all starters are replaced.


  • Check that if the engine cooling system uses internal zinc protection that the zincs are not corroded away.
  • Don’t leave batteries chargers on 24 hours a day 7 days a week , this only leads to trouble, if you have a built in charger , it’s only for convenience, use it if you haven’t been on the boat for a few weeks .
  • Checking for battery drain, disconnect positive terminal and lightly rub up against battery terminal ans see if you get a very slight, small spark , if so then something is draining the battery , check all cabin lights etc.

Electrolisis ~~~~~~~~ Stray Current (an explanation)

Stray current is electricity that is flowing where it’s not supposed to – through water, fittings on your boat, wet wood, damp surfaces, etc. It can be a shock hazard and it can cause corrosion (technically known as electrolytic corrosion).
Stray current corrosion is caused by a power source such as your batteries or the shore power connection. It is unlikely for serious corrosion to be caused by stray currents flowing through the water, without a metallic path to your boat.
Because of the relatively high driving voltages, stray current corrosion can act far more quickly than the corrosion caused by dissimilar metals in contact (galvanic corrosion).
Note: The word electrolysis is often mistakenly used to describe various kinds of corrosion. Electrolysis actually refers to the bubbling off of gases that occurs with electrolytic corrosion.
Please call us @ 619.578.5979 or feel free to stop by and visit us @ 1215 Beardsley St. San Diego 92113 and you will find that we ourselves are a group of extremely knowledgeable and like minded boaters. We are more than willing to provide you with professional boat service that is above all others.