1979-1983 mercury 70 hp battery cables

I am replacing my battery cables on my '79-'83 Mercury 70 HP.(no serial #) The old and I think original battery cables were bad, i ordered up some 4 gauge marine cable, 7 foot of black and red. Only because thats the gauge that looked to be on there originally. But these new cables are way too thick, and won't slide in the spot where the cables enter the motor. There is a plastic/rubber piece where the cables come thru, and neg grounds like 2 to 3 inches above that spot, and positive goes up and over to starter. But, I'm wondering if 6 gauge would probably work or does anyone know if that will be too thick to slide into original spot where the cable goes through. Or should I go with 8 gauge? But I read somewhere that 6 gauge or even 4 gauge would be the best option. Thanks guys.

6 ga. runs about 1/4". Should be fine. That's what I use on bigger motors generally over 50 hp.

yea, thats what i kinda figured and plan on getting is 6 gauge marine wire, i hope it will fit in the spot i need it too. thanks.

Right, the smaller motors I use 8 ga. the little starters don't draw as many amps and often less battery cable length is needed. It helps to keep cables short and sweet....adjusted to your application. A finer weave copper, of course, will be more flexible and likely a higher quality jacket too. I have a 1957 Johnson Javelin with original cables......fine copper weave and pure rubber jacket (coating)......very flexible as well as durable, (obviously).