help with DS engine

[mcvltd]

Can anybody offer some help with setting up a DS engine on my boat?

I thought it was going to be really simple -

step1) add DS engine to scene
step2) position DS engine underwater and to the rear of the boat
step3) link DS engine to boat (boat is using DS dynamics for motion)
step4) alter 'force' parameter to suit velocity

...but.... nothing happens.

Have I missed a step... like 'start engine'?

Thanks in advance,

Rob.