I decided to do a mid-winter start up to run and flush the motor and found I have another starting/starter problem. This was the original issue when I bought the boat and it took me a full season and 3 starters, new battery cables, new dual batteries and a new starter solenoid to sort out. Here we go again...
Since dry-docking the boat in September, I have kept both the batteries on trickle chargers to keep them fresh. But when I went to start the motor both fully charged batteries were unable to turn the motor. The starter was able to rotate the motor about 1/4 of a turn and stopped. When I removed the plugs the motor would turn freely. But the batteries could not turn-over the motor!
The Starter Isn't Getting Enough Amps
Wondering if I might have a bad cell in a battery, I took my Jump Starter/Charging station and dialed it to 40 Amps and connected it to the #1 battery. I was still unable to turn the motor. Next I took the Jump Starter/Charging station and connected the positive clamp to the starter relay and connected the negative clamp to the starter body. (These are the two positions the battery cables connect to the motor.) Essentially I by-passed the battery cables. Then I turned the key and the starter spun the motor robustly and the motor roared to life!
One of the symptoms I've had is the starter getting very hot. I'm told this is a result of the starter not getting enough Amps so the loss of amperage in the cables would make sense.
Here are my old battery cables. They were made from a #6 gauge jumper cable with crimped-on auto-parts store ends. (Its the orange and black cable, ignore the arrow it is pointing to cotter pins.)
Go Big on the Battery Cables
I decided it was time to upgrade the battery cables. Originally I had made a set of cables using a set of #6 gauge battery jumper cable purchased from the local car parts store. I cut the clamps off and crimped on bronze battery cable ends. Since I am running a pair of marine starting batteries I should have 2000 cranking Amps and this should be plenty to turn this starter/motor. I did some research and found there are several factors including the diameter of the cable, length of the cable and the quality of the connections that work against long battery cables. I have all three going against me.
I found a website that recommended to get 100 Amps through a 15' cable you need at least a 1/0 gauge cable. Not 6, not 4, not 2, not 1 gauge... 1/0! And they suggested 2/0 to be safe. I found a seller on E-bay that makes custom marine quality cables and ordered a pair of 2/0 cables for just shy of $185. They called and warned me these cables are 5/8" diameter each. When the cables arrived they were impressive (and heavy). I worried I wouldn't be able to run them around the motor under the cowl.
I spent the better part of a day re-running the cables and neatly attaching them to my batteries and to the starter solenoid and starter. Guess what? I turned the key, the starter spun the motor and she fired right up!. The moral to this story... a #6 battery cable is like a straw and two 1000 Amp batteries are like a fire hydrant. The 2/0 cables are likely over kill but they are more like the fire hose I needed.
The battery cables on my 15' boat are 15' feet long! The positive cable starts a couple feet from the stern on the port side of the boat at the battery on/off switch. The negative cable is on a ground buss on the back side of the board where the on/off switch is mounted.
The battery cables go back to the stern and across the transom and they are attached on the starboard side of the boat where they then pass through the cable hole in the splash well.
They pass into the motor housing along with the fuel line and then around the front of the motor and down the starboard side of the motor.
The negative cable runs under the starter is grounded to the motor at the starter bracket.
The positive cable goes all the way back and is attached to the rear side of the starter solenoid.
In all that's a 15' journey for the amps to travel.