battery cable replacement to f115

[rocket350]

My rectifier was replaced last year and now I'm having charging issues again. I was about to bolt on a new rectifier but I decided to investigate further. The engine has always cranked slowly so I decided to use a battery tester that draws 100 amps. Battery's are good and fully charged from the on board trickle charger. I hooked it up the the power posts under the floor where the battery cables meet the cables leading to the engine and checked out "good." I then hooked it up to the starter post and ground on the engine and it reads not "weak," but "bad."

So I am guessing bad cables to the motor. I cleaned all posts and contacts last year with no difference. Like I said, she always cranks slow like a weak starter or battery. I am assuming this is why I am having issues with the rectifier/regulator. With a multimeter the voltage drops to 9 volts while cranking.

Do I have to purchase Yamaha cables or can I use automotive? I would seal them up on the ends.

[boscoe99]

You do not have to use Yamaha cables. Many don't, even boat builders who are installing brand new motors.

If you can get away with a shorter length cable then all the better.

Just use an appropriately rated wire size and if it were me I would both crimp and solder the terminals to the cables.

But don't guess. Put a voltmeter on the battery itself. Check the voltage while the motor is being cranked. Should be no less than 10.5 volts. Higher is better of course.

Do a voltage drop test to determine how much voltage is being lost from the battery to the solenoid when the motor is being cranked. If you don't know how to do the test holler and I will post a diagram for you.

Switches, posts, terminals and such along the way from the battery to the motor can be problematic.

[rocket350]

Well I'll be.... looks like my batteries are just weak. Its reading about 12.5 at battery with a multimeter. 12.45 with ignition on and about 10v while cranking. At the motor it drops to about 8v while cranking.

[boscoe99]

Seems to be two problems. Bad battery and possibly bad cabling. Get the battery replaced first and then check for cranking voltage at the solenoid. Two volts drop is too much. But, with a new good battery that might change.

[rocket350]

I put in a brand new battery with 675 CCA and it turns over a lot better and sounds normal. Put the multimeter on the battery while cranking and holds at 12.6. At the power posts under the floor 10.5 and at the motor 8.9. Grrrrrrrr...

I have the meter right on the wires - ground on the block and the positive on the starter before going to the solenoid.

I am going to check the battery switch next but it looks like I'm going to need to replace the cables.

[99yam40]

Don't forget to check the ground cable and connections also.


Hooking volt meter leads between different components while under load will show where the higher voltage drop ( bad connection) is.
So would not need to replace everything, just where the problem is located