Engine is a Rolls Royce B81 straight eight, gas, about 400ci, though a few were modified for diesel (ex. Perkins)
A few years ago a pal in the UK said he had a friend who worked at the factory (60's?). That guy said they would drive them off the pier. If the went at least 30mph and the water was no more that 5' down they would alway come back up. Makes me wonder how many sank finding those figures.
What is amazing is the load place on the windshield, and what would happen if it were to fail.
Here is a vintage pic ot the some army sea trials. looks like a PT boat making the waves. I thought this was the Swedish or Norwiegain Army but pic lable says prototype and my memory isn't always reliable.
Here is a third pic, factory of a leak test, note the simulated cargo.These were rated for 5 tonnes land and 4 tonnes marine,
Oh, BTW anything MV related is welcome here