Assuming to double speed the force has to increase by a factor of eight. That hurts if you want to go fast but helps if you only need to go very slow.

Assume 30 tons pull by tug could tow that ship at 7 kts or so. Redoing I get under the 0.1 tons capacity for the car at:

0.9 kts = 0.06 tons. So top speed with the car will be around 1 kt.

But the issue here is acceleration. With F= ma and F is small and m is very big than a is going to be small.

Convert 0.13 tons of drawbar force to newtons is about 1300 N, 13,000 tons is 13,000,000 kgs then we will get a in m/s^2

That gives 1300N/13,000,000kg = 0.0001 m/s^2,

0.1 kt which should be easy to see (about a foot ever 5 seconds) is about 0.05 m/s

It will take about five minutes ((300 secs) to get up to 0.1 kt assuming no water resistance.

I’m a bit rusty, look about right @dbeierl?