3 wire to 2 wire tilt/trim?

[Grant Brown]

1987 70 hp 3 cyl. S/N 0A739874. 3 wire, square body, 3 ram, side fill tilt/trim unit.

I found a very good deal on a 1997 2 wire, round body rear fill unit replace my 3 wire. Everything looks like it will fit, but how do I rewire the electric motor?

3 wire - Blue is up, green is down and the black is for ground.
2 wire - same only grounded through the body of the motor?

Thanks,
Grant