Power trim down question

[hap777]

I recently had my boat motor winterized. i asked the mechanic to remove the battery from the boat as i wanted tto keep it warm in the house for the winter. He did that, but now I want to power trim the motor vertical (down), but not sure which cable in the boat is negative or which one is positive. I need to know this as I plan to hook up booster cables from my car to the cables in the boat to power down the motor. (Or is that not a good idea?)
How would you do it?

Thank you

 

[alldodge]

One should be red and the other black
Not knowing what you have, the Positive will come from the starter post and Negative will come from the Block