In the eighties I built a 63-foot staysail schooner. Used a four valve 6-71 for main power. Pushed it nearly to hull speed
with power to spare. It also ran the refrigeration
for two cold holds plus all the hydraulics, etc.
While they are a two-stroke don’t compare a two-stroke diesel
to a two-stroke gas. The blower on a Jimmy completely exhausts the combustion chamber on each stroke. They accelerate rapidly and while they don’t have the longevity of the older Cats or Cummings they would go for 10,000 hours or so.
The big issue was the fuel
economy and it stinks! They tend to suck fuel
when pulling a load. I remember a couple of fireboats at Long Beach in the 90’s that had 12V-92’s for propulsion
and main pumps, so ran three total. Would hate to buy the fuel!
Ran some 12V’s on gensets on a job once but they used much more fuel than the Cat D277's.
Other than fuel, they start easily and run very smoothly if the rack is set correctly. There is no injector pump
on a Detroit but each individual injector must be timed.
Yes, at 1800(full governed rpm) you can hear the blower. Sound as if they are ready to self-destruct because they are firing every rev.
One advantage to the two stroke series is that they can run either clockwise or counter-clockwise with different starters and change the oil
pump gears around. That made it easy to have opposite port and starboard prop rotation.
The old days,