Re: Battery problem
In short: I have a palsy 90 hp Merc 2 cycle OB. Lots of current sucking monsters out there that would put my starting current to shame....those with out reduction gears which crank more slowly so that they don't suck up so many amperes.
Manual says mine could suck up to 120 amps to start (OEM manual, Merc P/N 90-830234R3, Sheet 1A-2))
Okaye, you have a 12 volt battery, actually around Dallas, Texas it's normally about 12.75 V measured with a digital DMM for a full charge at STP (Standard Temperature and Pressure).
Using 12v as a number, you need about 10V across your starter to get the Bendix spinning enough so that it can engage the flywheel, spin it adequately at a sufficient speed to start the engine to rotating and all that stuff so that it will start for as long as it takes it to make up it's mind that if feels like starting....first starts of the day in particular.
So we are essentially looking at 2 Volts of potential, divided by 120 amperes of current, which leaves 0.1 ohms of resistance that the whole starting circuit...battery + to engine, through engine starting solenoid, through starter, to starter ground, back to the battery negative...Phew. Ohms law states that "1 Ampere of current will flow through 1 Ohm of resistance driven by a difference of potential (Voltage) of 1 volt". That's the law and that's the way it is....fact.
If your terminals aren't clean, not on the outside, but on the inside where the current flows, and if your lugs crimped onto your wires that are connected to these terminals aren't in pristeen condition you can forget it.
Hope this helps.
Mark
