Originally Posted by
botters
possibly im just going off of something i read up about on two stroke motors the other week that highlighted one of the plus's of two strokes being able to run backwards and it mentioned one of the reasons being that some diesel boats ran backwards to reverse a prop
i also had a moped years ago with a dodgy coil that intermittently upon backfiring would run (albeit poorly) backwards which was interesting to ride lol!
Generalising here, but the big two strokes are generally fitted to long haul tankers/bulkers/container ships and run on awful fuel qualities and are very efficient. They are what are known as "slow speed diesels" running at ~100rpm
After that you get into medium and high speed diesels, which will have a gearbox by necessity, to reduce the 500-700pm crank speed down to shaft speed. These therefore normally have a reverse if on normal shafts.
If you go without conventional shafts, then you use Voith Schneider drives, or azimuth thrusters and things
After that you get more novel drive systems such diesel electric which are commonly used where there is a variable hotel load/propulsive load and it gives flexibility to manage both.